Semiconductor device and semiconductor device manufacturing method

ABSTRACT

Provided is a semiconductor device including a semiconductor substrate; a hydrogen donor that is provide inside the semiconductor substrate in a depth direction, has a doping concentration that is higher than a doping concentration of a dopant of the semiconductor substrate, has a doping concentration distribution peak at a first position that is a predetermined distance in the depth direction of the semiconductor substrate away from one main surface of the semiconductor substrate, and has a tail of the doping concentration distribution where the doping concentration is lower than at the peak, farther on the one main surface side than where the first position is located; and a crystalline defect region having a crystalline defect density center peak at a position shallower than the first position, in the depth direction of the semiconductor substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.16/799,733, filed on Feb. 24, 2020, which is a continuation ofInternational Patent Application No. PCT/JP2019/011180, filed on Mar.18, 2019, the entirety of each of which is incorporated herein byreference. The application also claims priority from the followingJapanese patent application, which is explicitly incorporated herein byreference:

-   -   No. 2018-051655 filed in JP on Mar. 19, 2018.

BACKGROUND 1. Technical Field

The present invention relates to a semiconductor device and asemiconductor device manufacturing method.

2. Related Art

A conventional semiconductor device such as an insulated gate bipolartransistor (IGBT) is known, as shown in Patent Document 1, for example.

-   Patent Document 1: US Patent Application Publication 2005/0116249

In a semiconductor device, it is preferable to control the carrierlifetime.

SUMMARY

According to a first aspect of the present invention, provided is asemiconductor device. comprising a semiconductor substrate. Thesemiconductor device may include a hydrogen donor. The hydrogen donormay be provided inside the semiconductor substrate in a depth direction,and may have a doping concentration that is higher than a dopingconcentration of a dopant of the semiconductor substrate. The hydrogendonor may have a doping concentration distribution peak at a firstposition that is a predetermined distance in the depth direction of thesemiconductor substrate away from one main surface of the semiconductorsubstrate. The hydrogen donor may have a tail in the dopingconcentration distribution where the doping concentration is lower thanat the peak, farther on the one main surface side than where the firstposition is located. The semiconductor device may comprise a crystallinedefect region having a crystalline defect density center peak at aposition shallower than the first position, in the depth direction ofthe semiconductor substrate.

The semiconductor substrate may include a drift region of a firstconductivity type provided to include the first position. Thesemiconductor substrate may include an anode region of a secondconductivity type provided between the drift region and one main surfaceof the semiconductor substrate.

The semiconductor substrate may include a buffer region of a firstconductivity type and a higher doping concentration than the driftregion, between the drift region and the other main surface of thesemiconductor substrate.

A doping concentration distribution of the hydrogen donor may have donorpeaks at a plurality of positions in the buffer region. The crystallinedefect region may have a crystalline defect density center peak, betweena plurality of donor peaks of the hydrogen donor, in the depth directionof the semiconductor substrate.

The doping concentration distribution of the hydrogen donor may havedonor peaks at a plurality of positions in the buffer region. Thecrystalline defect region may have a center peak of the crystallinedefect density farther on the other main surface side of thesemiconductor substrate than where the plurality of donor peaks of thehydrogen donors are located, in the depth direction of the semiconductorsubstrate.

The crystalline defect region may be provided from the center peak tothe one main surface, in the depth direction of the semiconductorsubstrate.

The doping concentration of the hydrogen donor concentrationdistribution at the first position may be greater than or equal to1×10¹⁴ (/cm³) and less than or equal to 1×10¹⁵ (/cm³).

The semiconductor device may comprise a transistor portion in which acollector region of a second conductivity type is provided in a regionin contact with the other main surface of the semiconductor substrate.The semiconductor device may comprise a diode portion in which a cathoderegion of a first conductivity type with a higher doping concentrationthan the concentration of the dopant in the semiconductor substrate isprovided in the region in contact with the other main surface of thesemiconductor substrate. The diode portion may include the firstcrystalline defect region. The transistor portion may include the firstcrystalline defect region. The transistor portion may include the firstcrystalline defect region in a region in contact with the diode portion.The semiconductor device may further comprise an edge terminationstructure portion arranged between an outer circumferential edge of thesemiconductor substrate and an active portion in which the transistorportion and the diode portion are provided, on a top surface of thesemiconductor substrate. The edge termination structure portion mayinclude the first crystalline defect region.

The crystalline defect density distribution may have a tail from thecenter peak toward the one main surface of the semiconductor substrate.The crystalline defect density of the anode region may be less than orequal to half of the crystalline density distribution at the centerpeak.

The crystalline defect density of the anode region may be the same as aminimum value of the crystalline defect density in the drift region.

According to a second aspect of the present invention, provided is asemiconductor device manufacturing method. The manufacturing method maycomprise a step of implanting hydrogen ions in a depth direction of asemiconductor substrate through one main surface of the semiconductorsubstrate. The manufacturing method may comprise a step of annealing thesemiconductor substrate at a first temperature. The annealing step mayreduce the crystalline defects generated at a position where thehydrogen ion implantation causes a maximum hydrogen concentration. Theannealing step may form a position where a defect density of crystallinedefects formed by the hydrogen ion implantation is at a maximum valuefarther on the one main surface side than where a position of themaximum hydrogen concentration is located.

The manufacturing method may comprise, before the step of implantinghydrogen ions in the depth direction of the semiconductor substratethrough the one main surface side of the semiconductor substrate, a stepof implanting hydrogen ions in the depth direction of the semiconductorsubstrate through the other main surface side of the semiconductorsubstrate. The manufacturing method may comprise, before the step ofimplanting hydrogen ions in the depth direction of the semiconductorsubstrate through the one main surface side of the semiconductorsubstrate, a step of annealing the semiconductor substrate, into whichthe hydrogen ions have been implanted from the other main surface, at asecond temperature that is higher than the first temperature.

The step of implanting hydrogen ions in the depth direction of thesemiconductor substrate through the other main surface side of thesemiconductor substrate may include a step of implanting the hydrogenions a plurality of times, such that peaks of a hydrogen ionconcentration distribution are at different positions in the depthdirection of the semiconductor substrate.

The manufacturing method may comprise a step of forming thesemiconductor substrate into chips after the step of annealing at thefirst temperature. The manufacturing method may comprise a solderingstep of soldering the semiconductor substrate that has been formed intochips at a third temperature onto a circuit board. The third temperaturemay be lower than the first temperature.

In the step of implanting the hydrogen ions, the hydrogen ions may beimplanted with an acceleration energy resulting in a range of 8 μm ormore from the one main surface of the semiconductor substrate.

An acceleration energy in the step of implanting the hydrogen ions maybe greater than or equal to 1.0 MeV. The acceleration energy may begreater than or equal to 1.5 MeV. An acceleration energy in the step ofimplanting the hydrogen ions may be less than or equal to 11.0 MeV. Theacceleration energy may be less than or equal to 5.0 MeV. Theacceleration energy may be less than or equal to 2.0 MeV.

The dose amount of the hydrogen ions in the step of implanting thehydrogen ions may be greater than or equal to 1.0×10¹²/cm². The doseamount of the hydrogen ions in the step of implanting the hydrogen ionsmay be less than or equal to 1.0×10¹⁵/cm².

The summary clause does not necessarily describe all necessary featuresof the embodiments of the present invention. The present invention mayalso be a sub-combination of the features described above.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1A is a top surface view of an example of a semiconductor device100 according to one embodiment of the present invention.

FIG. 1B shows an example of a portion of the semiconductor device 100 ina YZ cross-sectional plane.

FIG. 2 shows a cross section of a semiconductor device 150 serving as acomparative example.

FIG. 3 shows distributions of each of the net doping concentration (A),the hydrogen concentration and the helium concentration (B), thecrystalline defect density (C), the carrier lifetime (D), the carriermobility (E), and the carrier concentration (F), along the line a-a′ inthe semiconductor device 100 according to the embodiment shown in FIG.1B and along the line z-z′ in the semiconductor device 150 of thecomparative example.

FIG. 4 shows another example of a cross section of the semiconductordevice 100 according to the present embodiment.

FIG. 5 shows another example of a cross section of the semiconductordevice 100 according to the present embodiment.

FIG. 6 shows another example of a cross section of the semiconductordevice 100 according to the present embodiment.

FIG. 7A shows distributions of each of the net doping concentration (A),the hydrogen concentration (B), the crystalline defect density (C), thecarrier lifetime (D), the carrier mobility (E), and the carrierconcentration (F), along the line c-c′ in the semiconductor device 100according to the embodiment shown in FIG. 5.

FIG. 7B shows distributions of each of the net doping concentration (A),the hydrogen concentration (B), the crystalline defect density (C), thecarrier lifetime (D), the carrier mobility (E), and the carrierconcentration (F), in a case where the crystalline defect region 19-2 onthe bottom surface 23 side is formed by implanting helium ions.

FIG. 7C shows distributions of each of the net doping concentration (A),the hydrogen concentration (B), the crystalline defect density (C), thecarrier lifetime (D), the carrier mobility (E), and the carrierconcentration (F) of another example.

FIG. 7D shows distributions of each of the net doping concentration (A),the hydrogen concentration (B), the crystalline defect density (C), thecarrier lifetime (D), the carrier mobility (E), and the carrierconcentration (F) of another example.

FIG. 8A is a partial view of an example of a top surface of asemiconductor device 200 according to the present embodiment.

FIG. 8B is a partial view of another example of a top surface of thesemiconductor device 200.

FIG. 8C is a partial view of another example of a top surface of thesemiconductor device 200.

FIG. 8D is a partial view of another example of a top surface of thesemiconductor device 200.

FIG. 9A shows an example of the d-d′ cross section in FIG. 8A.

FIG. 9B shows an example of the d-d′ cross section in FIG. 8B.

FIG. 9C shows an example of the d-d′ cross section in FIG. 8C.

FIG. 10A shows an example of an outline of a semiconductor devicemanufacturing method according to the present embodiment.

FIG. 10B shows another example of the semiconductor device manufacturingmethod.

FIG. 11 shows another example of the semiconductor device manufacturingmethod according to the present embodiment.

FIG. 12 shows distributions of each of the hydrogen concentration (B),the crystalline defect density (C), and the carrier concentration (F),along the h-h′ line in FIG. 11.

FIG. 13 shows another example of the semiconductor device manufacturingmethod according to the present embodiment.

FIG. 14 shows another example of the semiconductor device manufacturingmethod according to the present embodiment.

FIG. 15 shows another example of an outline of the semiconductor devicemanufacturing method according to the present embodiment.

FIG. 16 is a diagram describing the step of forming the crystallinedefect region 19 and the high concentration region 26 by implantinghydrogen ions (protons in the present example) from the top surface 21side of the semiconductor substrate 10.

FIG. 17 is s a diagram describing the step of forming the crystallinedefect region 19 and the high concentration region 26 by implantinghydrogen ions (protons in the present example) from the bottom surface23 side of the semiconductor substrate 10.

FIG. 18 shows distribution diagrams, in the depth direction, of the netdoping concentration (A), the hydrogen concentration (B), thecrystalline defect density (C), the carrier lifetime (D), the carriermobility (E), and the carrier concentration (F) in the semiconductordevice 100 shown in FIG. 17.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, some embodiments of the present invention will bedescribed. The embodiments do not limit the invention according to theclaims, and all the combinations of the features described in theembodiments are not necessarily essential to means provided by aspectsof the invention.

In this specification, one side of the semiconductor substrate in onedirection parallel to a depth direction is referred to as the “top” andthe side of the semiconductor substrate in the other direction parallelto the depth direction is referred to as the “bottom”. Among the twosurfaces of each of a substrate, layers, and other components, onesurface is referred to as the “top surface” and the other surface isreferred to as the “bottom surface.”

The directions of the “top” and “bottom” are not limited to thedirection of gravity or to the direction of attachment to the substrateor the like when the semiconductor device is implemented.

In this specification, there are cases where technical concepts aredescribed using orthogonal coordinate axes of the X-axis, the Y-axis,and the Z-axis. In this specification, a plane parallel to the topsurface of the semiconductor substrate is the XY-plane, and a depthdirection that is perpendicular to the top surface of the semiconductorsubstrate is the Z-axis.

In each embodiment, an example is described in which a firstconductivity type is N type and a second conductivity type is P type,but instead a first conductivity type may be P type and a secondconductivity type may be N type. In this case, the conductivity type ofeach substrate, layer, region, and the like in each embodiment may havethe opposite polarity. Furthermore, when P+ type (or N+ type) is used inthis specification, this means that the doping concentration is higherthan when P type (or N type) is used, and when P− type (or N-type) isused, this means that the doping concentration is lower than when P type(or N type) is used.

In this specification, the doping concentration refers to theconcentration of impurities that have become donors or acceptors. Inthis specification, the difference between the concentration of thedonors and the concentration of the acceptors (that is, the net dopingconcentration), may be referred to as the doping concentration.Furthermore, the peak value of the doping concentration distribution ina doping region may be referred to as the doping concentration in thisdoping region.

FIG. 1A is a top surface view of an example of a semiconductor device100 according to one embodiment of the present invention. Thesemiconductor device 100 includes a semiconductor substrate 10. Thesemiconductor substrate 10 may be a silicon substrate, a silicon carbidesubstrate, a nitride semiconductor substrate such as a gallium nitridesubstrate, a diamond semiconductor substrate, or an oxide semiconductorsubstrate such as a gallium oxide substrate. The semiconductor substrate10 in the present example is a silicon substrate. In FIG. 1A, the endportion at the periphery of the semiconductor substrate 10 is aperipheral edge 140.

The semiconductor device 100 includes an active portion 120 and an edgetermination structure portion 92. The active portion 120 is a region inwhich a main current flows between the top surface and the bottomsurface of the semiconductor substrate 10 when the semiconductor device100 is controlled to be in the ON state. In other words, the activeportion 120 is a region in which current flows in the depth directioninside the semiconductor substrate 10, from the top surface to thebottom surface of the semiconductor substrate 10 or from the bottomsurface to the top surface of the semiconductor substrate 10. Aninterlayer dielectric, an emitter electrode, and the like, which aredescribed further below, are provided above the active portion 120, butare omitted from FIG. 1A. The region covered by the emitter electrodemay be the active portion 120.

At least one of a transistor portion 70 and a diode portion 80 isprovided in the active portion 120. The transistor portion 70 includes atransistor such as an insulated gate bipolar transistor (IGBT). Thediode portion 80 includes a diode such as a free wheel diode (FWD). Inthe example of FIG. 1A, transistor portions 70 and diode portions 80 arearranged along a prescribed arrangement direction (Y-axis direction).The transistor portions 70 and the diode portions 80 may be arranged incontact with each other in an alternating manner along the arrangementdirection. In the active portion 120, a transistor portion 70 may beprovided at each end in the Y-axis direction. In another example, thediode portion 80 may be provided in the active portion 120 while thetransistor portion 70 is not provided in the active portion 120.

Each diode portion 80 is provided with an N+ type cathode region, in aregion in contact with the bottom surface of the semiconductor substrate10. In FIG. 1A, the diode portions 80 indicated by solid lines areregions where the cathode region 82 is provided on the bottom surface 23of the semiconductor substrate 10. In the semiconductor device 100 ofthe present example, among the regions in contact with the bottomsurface of the semiconductor substrate 10, a collector region 22 isprovided in the region that is not the cathode region 82.

The diode portions 80 are regions where the cathode region 82 isprojected in the Z-axis direction. The transistor portions 70 areregions where the collector region 22 is provided on the bottom surfaceof the semiconductor substrate 10 and unit structures, which eachinclude an emitter region and a gate trench portion described furtherbelow, are provided periodically on the top surface of the semiconductorsubstrate 10. Extending regions 81 (the portions indicated by the dashedlines extending from the diode portions 80 in FIG. 1A) in which theregions where the cathode region 82 is projected extend in the X-axisdirection to the end portion of the active portion 120 or the gaterunner 48, may also be included in the diode portions 80.

The semiconductor device 100 of the present example further includes agate metal layer 50 and a gate runner 48. Furthermore, the semiconductordevice 100 may include pads such as a gate pad 116 and an emitter pad118. The gate pad 116 is electrically connected to the gate metal layer50 and the gate runner 48. The emitter pad 118 is electrically connectedto the emitter electrode 52.

The gate metal layer 50 may be provided surrounding the active portion120 in the top surface view of the semiconductor substrate 10. The gatepad 116 and the emitter pad 118 may be arranged within the regionsurrounded by the gate metal layer 50. The gate metal layer 50 may beformed of a metal material such as aluminum or an aluminum-siliconalloy. The gate metal layer 50 is insulated from the semiconductorsubstrate 10 by an interlayer dielectric film. Furthermore, the gatemetal layer 50 is provided to be separated from the emitter electrode.The gate metal layer 50 transmits the gate voltage applied to the gatepad 116 to the transistor portions 70.

The gate runner 48 connects the gate metal layer 50 and the transistorportions 70. The gate runner 48 may be formed of a semiconductormaterial such as polysilicon doped with impurities. A portion of thegate runner 48 may be provided above the active portion 120. The gaterunner 48 shown in FIG. 1A is provided traversing the active portion 120in the Y-axis direction. In this way, it is possible to restrict delaysand a decrease in the gate voltage even at the inside of the activeportion 120, which is distanced from the gate metal layer 50. A portionof the gate runner 48 may be arranged surrounding the active portion120, along the gate metal layer 50. The gate runner 48 may be connectedto the transistor portion 70 at an end portion of the active portion120.

The edge termination structure portion 92 is provided between the activeportion 120 and the peripheral edge 140 of the semiconductor substrate10, on the top surface of the semiconductor substrate 10. In the presentexample, the gate metal layer 50 is arranged between the edgetermination structure portion 92 and the active portion 120. The edgetermination structure portion 92 may be arranged with an annular shapesurrounding the active portion 120 on the top surface of thesemiconductor substrate 10. The edge termination structure portion 92 ofthe present example is arranged along the peripheral edge 140 of thesemiconductor substrate 10. The edge termination structure portion 92relaxes the electric field concentration on the top surface side of thesemiconductor substrate 10. The edge termination structure portion 92has a guard ring, a field plate, a RESURF, and a structure in whichthese components are combined, for example.

FIG. 1B shows an example of a portion of the semiconductor device 100 ina YZ cross-sectional plane. In the present example, part of a diodeportion 80 described in FIG. 1A in the YZ cross-sectional plane isshown. As described above, the semiconductor device 100 may be a chip inwhich the diode portion 80 shown in FIG. 1B is provided in the activeportion 120 and a transistor portion 70 is not provided, or may be achip in which both the diode portion 80 and the transistor portion 70are provided in the active portion 120. In the case of either chip, thediode portion 80 may have the same structure as in the semiconductordevice 100 described in FIGS. 1B to 7D. Furthermore, in the same manneras the semiconductor device 100 described in FIGS. 9A to 9C, 16, and 17,the diode portion 80 may include a dummy trench portion 30. In FIG. 1Bshowing the present example, the dummy trench portion 30 is omitted. Thedummy trench portion 30 does not need to be included in the diodeportion 80. The semiconductor device 100 of the present example includesthe semiconductor substrate 10, a top-surface-side electrode 53, and abottom-surface-side electrode 27. The top-surface-side electrode 53 isprovided on the top surface 21 of the semiconductor substrate 10. Thebottom-surface-side electrode 27 is provided on the bottom surface 23 ofthe semiconductor substrate 10. The top-surface-side electrode 53 andthe bottom-surface-side electrode 27 are formed of a conductive materialsuch as metal. The top surface 21 and the bottom surface 23 are the mainsurfaces of the semiconductor substrate 10.

The semiconductor substrate 10 includes a drift region 18 of a firstconductivity type. The drift region 18 of the present example is of N−type. The drift region 18 may be a region in the semiconductor substrate10 where other doping regions are not provided. The dopant of thesemiconductor substrate 10 may be N type donors such as phosphorus orantimony. As an example, the dopant of the semiconductor substrate 10 ofthe present example is phosphorus. The ratio of the donor concentrationto the chemical concentration of the dopant is referred to as the donoractivation ratio. The donor activation ratio of the dopant in thesemiconductor substrate 10 may be greater than or equal to 90% of thechemical concentration of the dopant and less than or equal to 100% ofthe chemical concentration of the dopant. The donor activation ratio ofthe phosphorus or antimony of the present example may be greater than orequal to 95% and less than or equal to 100%.

The doping concentration of the drift region 18 may match the dopingconcentration of the semiconductor substrate 10. If the dopingconcentration of the drift region 18 matches the doping concentration ofthe semiconductor substrate 10, the dopant of the drift region 18 maymatch the dopant of the semiconductor substrate 10. Alternatively, thedoping concentration of the drift region 18 may be two or more timeshigher than that of the doping concentration of the semiconductorsubstrate 10. In this case, the dopant of the drift region 18 may bedifferent from the dopant of the semiconductor substrate 10. As anexample, the dopant of the drift region 18 is hydrogen and the dopant ofthe semiconductor substrate 10 is phosphorus or antimony.

A single-crystal wafer of the semiconductor substrate 10 may bemanufactured from an ingot formed using the Czochralski method (CZmethod), the magnetic field application Czochralski method (MCZ method),the float zone method (FZ method), or the like. As an example, thesingle-crystal wafer of the semiconductor substrate 10 is a wafermanufactured using the magnetic field application Czochralski method(MCZ method).

An anode region 14 of a first conductivity type is provided above thedrift region 18. The anode region 14 of the present example is P− type,for example. The anode region 14 may be provided between the driftregion 18 and the top surface 21 in the Z-axis direction. In the presentexample, the top surface of the anode region 14 is provided in contactwith the top surface 21. Furthermore, in the present example, the anoderegion 14 is provided in contact with the drift region 18.

The cathode region 82 of a first conductivity type, which has a higherdoping concentration than the drift region 18, is provided below thedrift region 18. The cathode region 82 of the present example is N+type, for example. The cathode region 82 is provided in contact with thebottom surface 23. Furthermore, in the present example, the cathoderegion 82 and the drift region 18 are provided in contact with eachother. The cathode region 82 may be formed by implanting ions such asphosphorus ions through the bottom surface 23 of the semiconductorsubstrate 10 and performing annealing.

The semiconductor device 100 of the present example has a highconcentration region 26 provided inside the semiconductor substrate 10.The high concentration region 26 may be formed by implanting hydrogenions through the top surface 21. The hydrogen ions may be protons,deuterons, or tritons. The hydrogen ions are protons in the presentexample. The concentration distribution of the hydrogen in the depthdirection of the semiconductor substrate 10 has a concentrationdistribution peak at a first position Ps, which is a predetermineddistance DPs away from one main surface of the semiconductor substrate10 (the top surface 21 in the present example) in the depth direction ofthe semiconductor substrate 10. In FIG. 1B, the hydrogen concentrationdistribution peak at the first position Ps is indicated by the symbol(marker) “x”. The first position Ps may be arranged farther on the topsurface 21 side than ½ of the width of the semiconductor substrate.

The hydrogen concentration distribution in the depth direction of thesemiconductor substrate 10 has a hydrogen concentration tail, where theconcentration is less than the peak described above, farther on the topsurface 21 side than where the first position Ps is located. Thehydrogen concentration distribution and the concentration distributiontail are described further below.

The high concentration region 26 is provided in a range including thefirst position Ps. The high concentration region 26 includes hydrogendonors. The high concentration region 26 may include, as the hydrogendonors, VOH complex defects in which one or more hydrogen atoms (H), oneor more oxygen atoms (O), and one or more vacancies (V) are bonded in acluster. There are cases where the VOH complex defects become N typedonors. In this specification, the VOH complex defects are referred tosimply as hydrogen donors. Furthermore, there are cases where thechemical concentration of hydrogen is referred to as the hydrogenconcentration. The high concentration region 26 of the present exampleis N+ type, for example.

The oxygen of the semiconductor substrate 10 may be introducedintentionally, or may be introduced unintentionally. The oxygen of thesemiconductor substrate 10 may be introduced from an oxide film formedon a main surface of the semiconductor substrate 10. The oxygenconcentration of the semiconductor substrate 10 may be greater than orequal to 1×10¹⁶ (/cm³) and less than or equal to 1×10¹⁸ (/cm³), or maybe greater than or equal to 5×10¹⁶ (/cm³) and less than or equal to5×10¹⁷ (/cm³).

The hydrogen donors are formed after hydrogen ions are implanted througha main surface of the semiconductor substrate 10 (the top surface 21 inthe present example). After the implantation of the hydrogen ions, thedonor activation ratio of the hydrogen donors may be increased bythermally annealing the semiconductor substrate 10. By implanting thehydrogen ions, the hydrogen donors are formed in a region where thehydrogen concentration is at a maximum (that is, a region correspondingto a range Rp of the hydrogen ions). Furthermore, by annealing thesemiconductor substrate 10, the formation of the VOH complex defects isencouraged and the hydrogen donor concentration increases. In this way,the high concentration region 26 having a higher doping concentrationthan the drift region 18 is formed. The high concentration region 26 maybe formed in a manner to be sandwiched between the drift regions 18 inthe Z-axis direction (the depth direction perpendicular to the mainsurfaces of the semiconductor substrate 10). The method for forming thehigh concentration region 26 is described further below.

The first position Ps may be a peak position of the doping concentrationof the high concentration region 26, in the Z-axis direction. In thisspecification, there are cases where the peak of the hydrogen donorconcentration at the first position Ps is referred to as the donor peak.The doping concentration of the high concentration region 26 at thefirst position Ps may be greater than or equal to 1×10¹³ (/cm³) and lessthan or equal to 1×10¹⁷ (/cm³), may be greater than or equal to 1×10¹⁴(/cm³) and less than or equal to 1×10¹⁶ (/cm³), or may be greater thanor equal to 1×10¹⁴ (/cm³) and less than or equal to 1×10¹⁵ (/cm³).

A crystalline defect region 19-1 is provided above the highconcentration region 26. The crystalline defect region 19-1 may be aregion that includes crystalline defects formed due to the implantationof hydrogen ions through the top surface 21. In FIG. 1B, the range inthe Z-axis direction in which the crystalline defect region 19-1 isprovided is indicated by a double-sided arrow symbol.

The crystalline defect region 19-1 has a crystalline defect density peakat a position Ks that is a distance Dks away from the top surface 21 inthe Z-axis direction. The crystalline defect region 19-1 may be providedfrom the position Ks to the top surface 21. The crystalline defects maybe defects that serve as carrier recombination centers, and may bemainly composed of vacancies (V) and double vacancies (VV). Thecrystalline defect density may be the density of the recombinationcenters. Usually, dopants such as donors or acceptors are also includedin the crystalline defects, but in this specification, crystallinedefects refer to defects that mainly function as recombination centersto recombine carriers.

In the present example, the crystalline defect density peak of thecrystalline defect region 19-1 in the Z-axis direction is referred to asthe center peak. The position of the center peak in the Z-axis directionis the position Ks. The position Ks is provided at a position shallowerthan the first position Ps, which is the position of the dopingconcentration peak of the high concentration region 26, using the topsurface 21 as a reference. In other words, the distance Dks is less thanthe distance Dps. In FIG. 1B, the center peak of the crystalline defectdensity at the position Ks is indicated by the symbol (marker) “+”.

In the semiconductor device 100 of the present example, the carrierlifetime is controlled by the crystalline defects generated by thehydrogen ion implantation. In the present example, the region in whichthe lifetime is controlled (reduced) is provided at a different positionin the Z-axis direction than the position (range Rp) at which thehydrogen concentration has the maximum value, where the hydrogen ionsstop and the greatest amount of hydrogen is present. In the presentexample, the region in which the lifetime is reduced is a region that iscloser to the top surface 21 than the position where the hydrogenconcentration has the maximum value, in other words, a hydrogen ionpassed-through region. When the hydrogen ions pass through thesemiconductor substrate 10, these hydrogen ions collide with the atoms(silicon in the present) of the semiconductor, thereby having theirenergy attenuated and causing damage to the crystal, which forms a largenumber of crystalline defects in the region (passed-through region) thatis shallower than the range Rp of the hydrogen ions. In this way, thecrystalline defect region is formed in the hydrogen ion passed-throughregion, and the lifetime is controlled.

On the other hand, by having a large amount of hydrogen near theposition where the hydrogen concentration is at the maximum, thehydrogen terminates dangling bonds in vacancies and double vacancies.Therefore, in the vicinity of the position where the hydrogenconcentration is at the maximum, the recombination center density ismuch lower than in the passed-through region, and the effect on thecarrier recombination is almost nonexistent compared to this effect inthe passed-through region.

The center peak of the crystalline defect density in the crystallinedefect region 19-1 may be a top-surface-side lifetime control region 74.The top-surface-side lifetime control region 74 has a higher crystallinedefect density than other regions of the semiconductor substrate 10. Therange in which the lifetime control region of the present example isformed is described further below.

FIG. 2 shows a cross section of a semiconductor device 150 serving as acomparative example. The semiconductor device 150 of the comparativeexample differs from the semiconductor device 100 shown in FIG. 1B inthat the semiconductor device 150 is not provided with the highconcentration region 26 and is provided with a top-surface-side lifetimecontrol region 274 instead of the top-surface-side lifetime controlregion 74 in the semiconductor device 100 of the present example shownin FIG. 1B. The top-surface-side lifetime control region 274 is formedby implanting helium through the top surface 21.

In the semiconductor device 150 of the comparative example, thetop-surface-side lifetime control region 274 is provided at a positionKs' in the Z-axis direction. The distance Dks' in the Z-axis directionfrom the top surface 21 to the position Ks' is less than the distanceDks in the semiconductor device 100 shown in FIG. 1B.

When the helium ions and hydrogen ions are implanted through the topsurface 21 of the semiconductor substrate 10 with the same accelerationenergy, the hydrogen ions are implanted to a deeper position in thedepth direction of the semiconductor substrate 10 from the top surface21 than the helium ions. Therefore, the distance Dks is greater than thedistance Dks′.

In the semiconductor device 150 of the comparative example, the heliumimplanted into the semiconductor substrate 10 is barely activated asdonors in comparison to the hydrogen, even when annealing is performed.Therefore, in the semiconductor device 150 of the comparative example,the high concentration region 26 is not provided. Furthermore, unlikethe semiconductor device 100 of the present example, in thesemiconductor device 150 of the comparative example, there is nohydrogen (or the hydrogen concentration is extremely low) forterminating the dangling bonds present in the vacancies and doublevacancies, and therefore the peak position at which the crystallinedefect density is at a maximum, which is the recombination center,overlaps with the peak position of the helium concentration at which thelargest amount of helium is present in the semiconductor substrate 10.Therefore, the position at which the carrier recombination occurs mostfrequently is the peak position of the helium concentration.

FIG. 3 shows distributions of each of the net doping concentration (A),the hydrogen concentration and the helium concentration (B), thecrystalline defect density (C), the carrier lifetime (D), the carriermobility (E), and the carrier concentration (F), along the line a-a′ inthe semiconductor device 100 according to the embodiment shown in FIG.1B and along the line z-z′ in the semiconductor device 150 of thecomparative example. As described above, the top-surface-side lifetimecontrol region 74 is formed by implanting the hydrogen ions into thesemiconductor substrate 10 in the semiconductor device 100, and thetop-surface-side lifetime control region 274 is formed by implantinghelium ions into the semiconductor substrate 10 in the semiconductordevice 150. It should be noted that the net doping concentration (A)shows only an example of the semiconductor device 100. In FIG. 3, eachdistribution drawing for the semiconductor device 100 is indicated by asolid line, and each distribution drawing for the semiconductor device150 is indicated by a dashed line.

The vertical axes of the distribution drawings (A), (B), (C), (D), and(F) are each displayed in a logarithmic (log) scale, and the verticalaxis of the distribution drawing (E) is displayed in a linear scale. InFIG. 3, in each of the distribution drawings in which the vertical axisdisplays a logarithmic scale, the value on the vertical axis at thepoint of intersection with the horizontal axis is not 0, and is insteada prescribed value greater than 0. In each distribution drawing, thehorizontal axis is displayed in a linear scale. The horizontal axis ineach distribution drawing in FIG. 3 indicates the depth from the topsurface 21 of the semiconductor substrate 10.

The distribution drawing (A) shows the net doping concentrationdistribution of donors and acceptors that have been electricallyactivated (in other words, the distribution of the difference betweenthe donor concentration and the acceptor concentration). As shown inFIG. 1B, the net doping concentration has a peak (donor peak) at theposition Ps. In the present example, a region that includes the positionPs and has a higher net doping concentration than the drift region 18 isthe high concentration region 26. The high concentration region 26 maybe a region in which the net doping concentration is greater than ahalf-value of the net doping concentration at the position Ps. The peakconcentration of the net doping concentration of the high concentrationregion 26 at the position Ps is referred to as Np.

In the distribution drawing (A), the N type region in which the dopingconcentration is higher than the doping concentration N₀ of thesemiconductor substrate 10 is N+ type. In the present example, thedoping concentration of the drift region 18 provided at a positiondeeper than the high concentration region 26 matches the dopingconcentration N₀. The hydrogen ions implanted through the top surface 21of the semiconductor substrate 10 pass through the drift region 18provided between the anode region 14 and the high concentration region26. The doping concentration of this drift region 18 may become higherthan the doping concentration N₀ of the semiconductor substrate 10 dueto remaining hydrogen donors. The average value of the dopingconcentration of this drift region 18 may be less than or equal to threetimes the doping concentration N₀ of the semiconductor substrate 10.

An N type accumulation region 16 with a higher concentration than thedrift region 18 may be included between the anode region 14 and thedrift region 18. The accumulation region 16 is a portion where the donordopant is accumulated with a higher concentration than in the driftregion 18. Two or more accumulation regions 16 may be included in thedepth direction. The two or more accumulation regions 16 may have two ormore peaks in the doping concentration. The region between two adjacentpeaks may be N type. The two or more accumulation regions 16 may bekink-shaped.

The distribution drawing (B) shows the chemical concentration of theimplanted hydrogen or helium. The hydrogen concentration is shown forthe semiconductor device 100 and the helium concentration is shown forthe semiconductor device 150. As an example, the chemical concentrationof atoms can be measured using secondary ion mass spectrometry (SIMS).The helium and hydrogen concentrations have distributions in which theimplanted helium ions and hydrogen ions are diffused due to annealing.The degree of diffusion can be controlled according to the annealingtime, the annealing temperature, and the like. The hydrogenconcentration has a peak at the position Ps. The helium concentrationhas a peak at the position Dks′.

The hydrogen concentration is the chemical concentration of hydrogen,and the concentration at the position Ps of the peak where the hydrogenconcentration is highest is referred to as Hp. The peak concentration Hpof the hydrogen concentration is higher than the peak concentration Npof the net doping concentration at the position Ps. With a representingthe donor activation ratio of the hydrogen donors, Np=αHp, and α may befrom 0.001 to 0.5. In other words, there are cases where the hydrogenconcentration is one order of magnitude greater than the donorconcentration, and cases where the hydrogen concentration is two or moreorders of magnitude greater than the donor concentration.

As described above, the hydrogen concentration distribution has a tail Sfrom the peak position Ps toward one main surface (the top surface 21 inthe present example). The tail S refers to the concentrationdistribution having a gentler change, in a case where the hydrogenconcentration distribution in a region shallower than the peak positionPs is compared to the hydrogen concentration distribution in a regiondeeper than the peak position Ps. In other words, the hydrogenconcentration distribution has the tail S diminishing as moving towardthe main surface through which the hydrogen ions were implanted. Thetail S may reach the top surface 21, but does not need to reach the topsurface 21. Furthermore, as shown in the distribution drawing (A), bycomparing the average doping concentration of the drift region 18 on theside shallower than the high concentration region 26 to the averagedoping concentration of the drift region 18 on the side deeper than thehigh concentration region 26, it may be judged that the tail S of thehydrogen concentration distribution is present on the side with thehigher average doping concentration.

The distribution drawing (C) shows the crystalline defect density afterthe hydrogen ions or helium ions were implanted into the semiconductorsubstrate 10 and annealing was then performed with prescribedconditions. In the semiconductor device 150 into which the helium ionshave been implanted, the crystalline defect density distribution and thehelium concentration distribution have similar shapes. For example, theposition Dks' of the helium concentration peak and the position Ks' ofthe crystalline defect density peak match.

The position where the net doping concentration of the highconcentration region 26 substantially matches the doping concentrationN₀ of the semiconductor substrate 10 farther on the bottom surface 23side than where the position Ps is located is referred to as theposition Z₀. The crystalline defect density farther on the bottomsurface 23 side than where the position Z₀ is located may have asufficiently small value Nr₀. Having the crystalline defect density be asufficiently small value Nr₀ means that the crystalline defect densityhas a value low enough that the carrier lifetime does not become lessthan τ₀, which is described further below. As an example, with Nr₀representing the concentration of vacancies or double vacancies, at atemperature of 300 K, Nr₀ may be less than or equal to 1×10¹² atoms/cm³,less than or equal to 1×10¹¹ atoms/cm³, or less than or equal to 1×10¹⁰atoms/cm³. At the position J₀ of the pn junction between the anoderegion 14 and the drift region 18 or accumulation region 16, thecrystalline defect density may be higher than Nr₀.

The density of crystalline defects such as vacancies and doublevacancies that occur due to the helium ion implantation is highest inthe vicinity of the position Dks' at which the most helium ions areimplanted. As described above, there is almost no hydrogen in thesubstrate in the semiconductor device 150, and therefore the crystallinedefects barely decrease when annealing is performed. Therefore, thedistribution of the crystalline defect density remains the same beforeand after the annealing.

In contrast to this, in the semiconductor device 100 into which thehydrogen ions have been implanted, the crystalline defects areterminated by the hydrogen, and therefore the crystalline defect densitydistribution and the hydrogen concentration distribution have differentshapes. For example, the position Ps of the hydrogen concentration peakand the position Ks of the crystalline defect density peak do not match.The position Ks of the crystalline defect density peak of the presentexample is arranged farther on the top surface 21 side of thesemiconductor substrate 10 than where the hydrogen concentration peakposition Ps is located. The crystalline defect density may decreasemonotonically on the top surface 21 side of the position Ks. Thecrystalline defect density may decrease monotonically and more steeplyon the bottom surface 23 side of the position Ks than on the top surface21 side of the position Ks.

In the vicinity of the position Ps of the hydrogen concentration peak, alarge amount of hydrogen terminates the dangling bonds of the vacancies,double vacancies, and the like. Therefore, the crystalline defectdensity in the vicinity of the position Ps of the hydrogen concentrationpeak is much smaller than the crystalline defect density at the positionKs of the crystalline defect density peak. In this specification, awidth of the distribution indicating a concentration that is greaterthan 1% of the peak concentration (Hp) is referred to as 1% full widthor FW1% M. The vicinity of the peak position Ps may refer to a region ina range of the 1% full width centered on the peak position Ps. Theposition Ks of the crystalline defect density peak may be provided at aposition shallower than the range of the 1% full width centered on thepeak position Ps.

However, the distance D between the position Ks of the crystallinedefect density peak and the position Ps of the hydrogen concentrationpeak is determined according to the distance that the hydrogen diffuseswithin the semiconductor substrate 10 due to the annealing. The distanceD may be less than or equal to 40 μm, less than or equal to 20 μm, orless than or equal to 10 μm. The distance D may be greater than or equalto 1 μm, greater than or equal to 3 μm, or greater than or equal to 5μm. The distance D may be greater than or equal to the 1% full width ofthe hydrogen concentration. The distance D may be greater than or equalto the 1% full width of the net doping concentration at the position Ps.In this case, the 1% full width of the net doping concentration is thewidth of the peak at 0.01 Np. The range for the value of the distance Dmay be a combination of the upper limit values and lower limit valuesdescribed above. The crystalline defect density distribution can beobserved by measuring the density distribution of the vacancies anddouble vacancies, using the positron annihilation method, for example.

The distribution drawing (D) shows the carrier lifetime distributionafter the hydrogen ions or helium ions were implanted into thesemiconductor substrate 10 and annealing was then performed withprescribed conditions. In the semiconductor device 150 into which thehelium ions have been implanted, the carrier lifetime distribution has ashape obtained by inverting the vertical axis of the crystalline defectdensity distribution. For example, the position at which the carrierlifetime has the minimum value matches the center peak position Ks' ofthe crystalline defect density.

Also in the semiconductor device 100 into which the hydrogen ions areimplanted, the carrier lifetime distribution has a shape obtained byinverting the vertical axis of the crystalline defect densitydistribution. For example, the position at which the carrier lifetimehas the minimum value matches the center peak position Ks of thecrystalline defect density. In the region that is within a range of theFW1% M centered on the peak position Ps of the hydrogen concentration,the carrier lifetime of the semiconductor device 100 may have themaximum value τ₀. The maximum value τ₀ may be the carrier lifetime inthe drift region 18 farther on the bottom surface 23 side than where thehydrogen concentration peak position Ps is located.

The carrier lifetime may have a sufficiently large value τ₀ farther onthe bottom surface 23 side than where the position Z₀ is located. Thecarrier lifetime having the sufficiently large value τ₀ refers to acarrier lifetime in a case where defects made up mainly of vacancies ordouble vacancies or a lifetime killer are not intentionally introducedto the semiconductor substrate 10. At a temperature of 300 K, τ₀ may begreater than or equal to 10 μs or greater than or equal to 30 μs. As anexample, τ₀ is 10 μs. The carrier lifetime may be less than τ₀ at theposition J₀ of the pn junction between the anode region 14 and the driftregion 18 or accumulation region 16.

The distribution drawing (E) shows the carrier mobility distributionafter the hydrogen ions or helium ions were implanted into thesemiconductor substrate 10 and annealing was then performed withprescribed conditions. The carrier mobility, farther on the bottomsurface 23 side than where the position Z₀ is located, may be a mobilityN₀ in the case of an ideal crystalline structure. In a case of siliconat a temperature of 300 K, for example, the mobility μ₀ is 1360 cm²/(vs)for electrons and 495 cm²/(Vs) for holes. The carrier mobility may beless than N₀ at the position J₀ of the pn junction between the anoderegion 14 and the drift region 18 or accumulation region 16.

The distribution drawing (F) shows the carrier concentrationdistribution after the hydrogen ions or helium ions were implanted intothe semiconductor substrate 10 and annealing was then performed withprescribed conditions. The carrier concentration can be measured usingthe spread resistance measurement method (SR measurement method), forexample.

With the SR measurement method, the spread resistance is converted intothe specific resistance and the carrier concentration is calculated fromthe specific resistance. With the specific resistance being ρ (Ω·cm),the mobility being μ (cm²/(V·s)), the elementary charge being q (C), andthe carrier concentration being N (/cm³), N=1/(μqρ) is established.

In the SR measurement method, a value of the semiconductor substrate 10with an ideal crystalline state is used for the carrier mobility.However, when damage remains in the semiconductor substrate 10 due tothe ion implantation, the crystalline state of the semiconductorsubstrate 10 degrades and enters a disordered state, and the mobility isreduced in actuality. Properly, the reduced mobility should be used asthe mobility in the SR measurement, but it is difficult to measure thevalue of the decreased mobility. Therefore, in the SR measurement in theexample of the distribution drawing (F), the ideal value is used for themobility. Therefore, the denominator of the carrier concentrationequation described above increases, and the carrier concentrationdecreases. In other words, in the distribution drawing (F), the measuredcarrier concentration experiences an overall drop in the region throughwhich the hydrogen ions pass (the region from the bottom end of theanode region 14 to the high concentration region 26 of the semiconductorsubstrate 10). However, in the high concentration region 26 near therange Rp of the hydrogen ions, the hydrogen concentration is high, andtherefore, the disordered state is ameliorated due to the hydrogentermination effect, and the mobility approaches the value of thecrystalline state. In addition, hydrogen donors are formed. Therefore,the carrier concentration becomes higher than the carrier concentrationN₀ of the semiconductor substrate 10.

In the semiconductor device 150 into which the helium ions areimplanted, the carrier concentration becomes low in a narrow region inthe vicinity of the peak position Ks′ of the helium concentration (thatis, the vicinity of the peak position of the crystalline defectdensity). In a case where the crystalline defects are formed byimplanting helium ions into the semiconductor substrate 10, the peakposition of the helium concentration, the position where the carrierconcentration exhibits a local minimum, the peak position of thecrystalline defect density, and the position where the carrier lifetimeexhibits a local minimum all match the position Ks′.

Also in a case where the crystalline defects are formed by implantinghydrogen ions into the semiconductor substrate 10, there are many caseswhere the peak position Ps of the hydrogen concentration and the peakposition of the crystalline defect density match before the annealing.However, when the annealing is performed after the hydrogen ionimplantation, the hydrogen is diffused from the peak position of thehydrogen concentration toward the top surface 21 of the semiconductorsubstrate 10, and the hydrogen terminates the dangling bonds included inthe vacancies and double vacancies. Therefore, the crystalline defectdensity after the annealing decreases around the peak position Ps of thehydrogen concentration. Due to this, the carrier lifetime in thevicinity of the position Ps where the hydrogen concentration forms apeak increases to become approximately τ₀.

The lifetime control region (the top-surface-side lifetime controlregion 74 in the present example) may be a region in which the carrierconcentration becomes lower than the carrier concentration N₀ of thesemiconductor substrate 10, as shown in the distribution drawing (F), onthe main surface side (top surface 21 side in the present example) wherethe hydrogen concentration exhibits the tail from the peak, as shown inthe distribution drawing (B). Furthermore, the density distribution ofthe vacancies and double vacancies such as shown in the distributiondrawing (C) may be measured, and a region in which the vacancy anddouble vacancy density is higher farther on the top surface 21 side ofthe peak position Ps than on the bottom surface 23 side of the peakposition Ps may be the lifetime control region. Alternatively, a regionthat is a width (FW1% M) between two positions which sandwich theposition Ks of the maximum value and at which the vacancy and doublevacancy density distribution has 1% of the maximum value may be thelifetime control region. Yet further, the position Ks at which thecrystalline defect density has a peak in the manner described above maysimply be the lifetime control region.

FIG. 4 shows another example of a cross section of the semiconductordevice 100 according to the present embodiment. The semiconductor device100 of the present example differs from the semiconductor device 100shown in FIG. 1B in that hydrogen ions are implanted through the bottomsurface 23, the high concentration region 26 is provided on the bottomsurface 23 side, and a crystalline defect region 19-2 is provided on thebottom surface 23 side. The bottom surface 23 side refers to the regionon the bottom surface 23 side of the center of the semiconductorsubstrate 10 in the Z-axis direction.

In the semiconductor device 100 of the present example, the hydrogenconcentration distribution in the depth direction of the semiconductorsubstrate 10 has a concentration distribution peak at a first positionPb that is a predetermined distance Dpb away, in the depth direction ofthe semiconductor substrate 10, from one main surface of thesemiconductor substrate 10 (the bottom surface 23 in the presentexample). In FIG. 4, the peak of the hydrogen concentration distributionat the first position Pb is indicated by the symbol (marker) “x”. Thefirst position Pb may be arranged farther on the bottom surface 23 sidethan where ½ the thickness T of the semiconductor substrate is located.

The hydrogen concentration distribution in the depth direction of thesemiconductor substrate 10 has a concentration distribution tail S (seeFIG. 3) where the concentration is less than the peak described above,farther on the bottom surface 23 side than where the first position Pbis located. The first position Pb may be arranged below the firstposition Ps in the Z-axis direction.

In the semiconductor device 100 of the present example, thesemiconductor substrate 10 may include the high concentration region 26,where the doping concentration is higher than that of the drift region18, between the drift region 18 and the bottom surface 23 of thesemiconductor substrate 10. The high concentration region 26 is providedto include the first position Pb. The high concentration region 26 ofthe present example may be a region formed by annealing thesemiconductor substrate 10 into which hydrogen ions have been implantedthrough the bottom surface 23. By annealing the semiconductor substrate10 after implanting the hydrogen ions, the hydrogen is activated as adonor and the high concentration region 26 having a higher dopingconcentration than the drift region 18 is formed.

In the semiconductor device 100 of the present example, the highconcentration region 26 is provided in a manner to be sandwiched bydrift regions 18 in the Z-axis direction. Since the high concentrationregion 26 has a higher doping concentration than the drift region 18,the depletion layer that spreads from the bottom surface side of theanode region 14 can be prevented from reaching the cathode region 82.

The crystalline defect region 19-2 is provided below the highconcentration region 26. The crystalline defect region 19-2 may be aregion that includes crystalline defects formed by implanting hydrogenions through the bottom surface 23. In FIG. 4, the range in which thecrystalline defect region 19-2 is provided in the Z-axis direction isindicated by a double-sided arrow symbol.

The crystalline defect region 19-2 includes the center peak of thecrystalline defect density at a position Kb that is a distance Dkb awayfrom the bottom surface 23 in the Z-axis direction. The crystallinedefect region 19-2 may be provided from the position Kb to the bottomsurface 23.

In the present example, the peak in the Z-axis direction of thecrystalline defect density in the crystalline defect region 19-2 is thecenter peak. The position of the center peak in the Z-axis direction isthe position Kb. As described in FIG. 3, in a case where the crystallinedefects are formed by implanting hydrogen ions, the peak position of thecrystalline defect density is arranged on the side of the main surfacethrough which the hydrogen ions were implanted (the bottom surface 23 inthe present example), compared to the peak position of the hydrogenconcentration. Therefore, the position Kb is provided at a positionshallower than the first position Pb, which is the peak position of thedoping concentration of the high concentration region 26, using thebottom surface 23 as a reference. In other words, the distance Dkb isless than the distance Dpb. In FIG. 4, the center peak of thecrystalline defect density at the position Kb is indicated by the symbol(marker) “+”.

In the semiconductor device 100 of the present example, the carrierlifetime is controlled by the crystalline defects generated due to thehydrogen ion implantation. In the semiconductor device 100 of thepresent example, the center peak of the crystalline defect density inthe crystalline defect region 19-2 may be the bottom-surface-sidelifetime control region 78. The bottom-surface-side lifetime controlregion 78 has a higher crystalline defect density than the other regionsof the semiconductor substrate 10.

FIG. 5 shows another example of a cross section of the semiconductordevice 100 according to the present embodiment. In the semiconductordevice 100 of the present example, in addition to the configuration ofthe semiconductor device 100 shown in FIG. 1B, a buffer region 20 of afirst conductivity type with a higher doping concentration than thedrift region 18 is provided below the drift region 18. The buffer region20 of the present example is N+ type, for example. The buffer region 20may be provided between the drift region 18 and the bottom surface 23 inthe Z-axis direction. In the present example, the buffer region 20 isprovided in contact with the drift region 18. The buffer region 20 canfunction as a field stop region that prevents the depletion layer, whichspreads from the bottom surface side of the anode region 14, fromreaching the cathode region 82.

In the semiconductor device 100 of the present example, the hydrogenconcentration distribution has concentration distribution peaks at aplurality of positions in the buffer region 20. Specifically, there areconcentration distribution peaks at four locations that are a positionPb4, a position Pb3, a position Pb2, and a position Pb1, in order fromthe top surface side toward the bottom surface side of the buffer region20. In FIG. 5, the peaks of the hydrogen concentration distribution atthe plurality of positions in the Z-axis direction are indicated by thesymbol (marker) “x”. The buffer region 20 of the present example may bea region formed by annealing the semiconductor substrate 10 afterhydrogen ions have been implanted through the bottom surface 23 into thesemiconductor substrate 10 at the position Pb4, the position Pb3, theposition Pb2, and the position Pb1.

The semiconductor device 100 of the present example is provided with aplurality of crystalline defect regions 19. The crystalline defectregion 19-1 is provided on the top surface 21 side of the semiconductorsubstrate 10, and the crystalline defect region 19-2 is provided on thebottom surface 23 side of the semiconductor substrate 10.

The crystalline defect region 19-1 is a region including crystallinedefects formed by implanting hydrogen ions through the top surface 21.The crystalline defect region 19-1 is the same as the crystalline defectregion 19-1 shown in FIG. 1B. The crystalline defect region 19-2 is aregion including crystalline defects formed by implanting hydrogen ionsor helium ions through the bottom surface 23. The crystalline defectregion 19-2 is not a necessary configuration, and is a region that maybe included as needed. The crystalline defect region 19-2 may beprovided within the buffer region 20. In FIG. 5, the range in the Z-axisdirection in which the crystalline defect region 19-1 is provided isindicated by a double-sided arrow symbol.

The crystalline defect region 19-2 may include a center peak of thecrystalline defect density between a plurality of peaks of the hydrogenconcentration, in the depth direction of the semiconductor substrate 10.Specifically, the crystalline defect region 19-2 may include the centerpeak of the crystalline defect density at any one of a position betweenthe position Pb1 and the position Pb2, a position between the positionPb2 and the position Pb3, and a position between the position Pb3 andthe position Pb4, where the positions Pbs 1 to 4 are the peak positionsof the hydrogen concentration of the buffer region 20, in the Z-axisdirection. Furthermore, the entire crystalline defect region 19-2 may beprovided between any peak positions of the hydrogen concentration. Thecrystalline defect region 19-2 of the present example shows one examplein which the center peak of the crystalline defect density is includedat the position Kb between the position Pb1 and the position Pb2. InFIG. 5, the center peak of the crystalline defect density between theposition Pb1 and the position Pb2 is indicated by the symbol (marker)“+”.

In the semiconductor device 100 of the present example, the carrierlifetime is controlled with the crystalline defects generated due to thehydrogen ion implantation. In the semiconductor device 100 of thepresent example, the center peak of the crystalline defect density inthe crystalline defect region 19-2 is the bottom-surface-side lifetimecontrol region 78.

The crystalline defect region 19-2 of the present example includescrystalline defects formed by implanting hydrogen ions or helium ions tothe position Pb2 through the bottom surface 23. As described in FIG. 3,in a case where the crystalline defects are formed by implantinghydrogen ions, the peak position of the crystalline defect density isarranged on the side of the main surface through which the hydrogen ionswere implanted, compared to the peak position of the hydrogenconcentration.

FIG. 6 shows another example of a cross section of the semiconductordevice 100 according to the present embodiment. The semiconductor device100 shown in FIG. 6 differs from the semiconductor device 100 shown inFIG. 5 in that the bottom-surface-side lifetime control region 78 isprovided below the position Pb1 in the Z-axis direction. The crystallinedefect region 19-2 may be provided up to the bottom surface 23 of thesemiconductor substrate 10.

The position of the bottom-surface-side lifetime control region 78 inthe Z-axis direction can be adjusted by adjusting the order of the step(process) of implanting hydrogen ions to a plurality of positions in theZ-axis direction and the step of annealing the semiconductor substrate10 into which the hydrogen ions have been implanted. The hydrogen ionimplantation step and the annealing step are described further below.

FIG. 7A shows distributions of each of the net doping concentration (A),the hydrogen concentration (B), the crystalline defect density (C), thecarrier lifetime (D), the carrier mobility (E), and the carrierconcentration (F), along the line c-c′ in the semiconductor device 100according to the embodiment shown in FIG. 5. The vertical axis andhorizontal axis in each distribution drawing are the same as in thecorresponding distribution drawing in FIG. 3.

The distribution drawing (A) shows the net doping concentrationdistribution of donors and acceptors that have been electricallyactivated. As shown in FIG. 5, the buffer region 20 has dopingconcentration peaks (donor peaks) at the positions Pb4, Pb3, Pb2, andPb1. The high concentration region 26 has a doping concentration peak(donor peak) at the position Ps. The doping concentrations betweenrespective donor peaks may be higher than the doping concentration N₀ ofthe semiconductor substrate 10, or may be the same as this dopingconcentration N₀. In the present example, the doping concentration of atleast a portion of the region between the position Ps and the positionPb4 is the doping concentration N₀. The dopant of the semiconductorsubstrate 10 may be phosphorus or the like. The doping concentration N₀may be the N₀ described in the distribution drawing (A) of FIG. 3.

In the distribution drawing (A), the N type region in which the dopingconcentration is higher than the doping concentration of the driftregion 18 is N+ type. The doping concentration of at least a partialregion of the drift region 18 between the position Ps and the positionPb4 may be lower than the doping concentration of the drift region 18farther on the top surface 21 side than where the position Ps islocated. The hydrogen ions implanted through the top surface 21 of thesemiconductor substrate 10 pass through the drift region 18 on the topsurface 21 side. Therefore, the doping concentration of this driftregion 18 may become higher than the doping concentration N₀ of thesemiconductor substrate 10 due to the remaining hydrogen. The averagevalue of the doping concentration of the drift region 18 on the topsurface 21 side may be less than or equal to three times the dopingconcentration N₀ of the semiconductor substrate 10.

Hydrogen ions are implanted from the bottom surface 23 of thesemiconductor substrate 10 to the positions Pb4, Pb3, Pb2, and Pb1.Therefore, the doping concentration in a region farther on the bottomsurface 23 side than where the position Pb4 is located may be higheroverall than the doping concentration N₀ of the semiconductor substrate10. That is, the doping concentration (donor concentration in thepresent example) of the drift region 18 in the region sandwiched in thedepth direction by two hydrogen donor peaks (the hydrogen donor peaksrespectively at the position Ps and the position Pb4 in the presentexample) is the lowest. The doping concentration (donor concentration inthe present example) of the region sandwiched by these two hydrogendonor peaks is the doping concentration N₀ of the semiconductorsubstrate 10, and the doping concentration distribution may besubstantially flat. At these two hydrogen donor peaks, the dopingconcentration on the top surface 21 side from the position Ps and on thebottom surface 23 side from the position Pb4 may become higher than thedoping concentration N₀ of the semiconductor substrate 10. The cathoderegion 82 in the present example is formed by implanting and diffusingphosphorus.

The distribution drawing (B) shows the chemical concentration of theimplanted hydrogen. Each peak of the hydrogen concentration has a tailon the side of the main surface through which the hydrogen ions wereimplanted. In the present example, the hydrogen concentration peak atthe position Ps has a tail S on the top surface 21 side. In other words,the hydrogen concentration distribution of the present example decreasesgently and monotonically from the first position Ps to the top surface21, on the top surface 21 side. The tail S may be provided across thedrift region 18 and the anode region 14.

The hydrogen concentration distribution of the present example has atail where the change of the concentration distribution is steeper thanin the tail S, on the bottom surface 23 side from the first position Ps.In other words, the hydrogen distribution exhibits an asymmetricdistribution on the top surface 21 side of the first position Ps and thebottom surface 23 side of the first position Ps.

The hydrogen concentration peaks respectively at the positions Pb4, Pb3,Pb2, and Pb1 each have a tail S′ on the bottom surface 23 side. Thehydrogen concentration peaks respectively at the positions Pb4, Pb3,Pb2, and Pb1 each have a tail where the change of the concentrationdistribution is steeper than in the tail S′, on the top surface 21 side.In other words, the hydrogen concentration peaks respectively at thepositions Pb4, Pb3, Pb2, and Pb1 each exhibit an asymmetric distributionon the top surface 21 side of the corresponding position Pb4, Pb3, Pb2,or Pb1 and the bottom surface 23 side of the corresponding position Pb4,Pb3, Pb2, or Pb1.

The hydrogen concentration may have a minimum value between a position(position Ps in the present example) farthest on the bottom surface 23side among the positions where hydrogen ions have been implanted fromthe top surface 21 side and a position (position Pb4 in the presentexample) farthest on the top surface 21 side among the positions wherehydrogen ions have been implanted from the bottom surface 23 side. Theposition where the sum of the distribution of the diffusion of thehydrogen implanted to the position Ps and the distribution of thediffusion of the hydrogen implanted to the position Pb4 is smallest isthe position where the hydrogen concentration is at the minimum value.Alternatively, the position where the hydrogen concentration is at aminimum value may be in a region that is sandwiched by two hydrogendonor peaks (the position Ps and position Pb4 in the present example)and in which the doping concentration has the substantially flat dopingconcentration distribution indicating the doping concentration N₀ of thesemiconductor substrate 10.

The distribution drawing (C) shows the crystalline defect density afterthe hydrogen ions were implanted into the semiconductor substrate 10 andannealing was then performed with prescribed conditions. The crystallinedefect density distribution farther on the top surface 21 side thanwhere the position Ps is located is similar to the crystalline defectdensity distribution of the semiconductor device 100 shown in thedistribution drawing (C) of FIG. 3. The crystalline defect density Nr₀may be the Nr₀ described in the distribution drawing (C) of FIG. 3. Thecrystalline defect density has a peak at the position Ks that is fartheron the top surface 21 side than where the position Ps is located. Thecrystalline defect density may decrease monotonically farther on the topsurface 21 side than where the position Ks is located. The crystallinedefect density may decrease monotonically and more steeply on the bottomsurface 23 side of the position Ks than on the top surface 21 side ofthe position Ks.

The crystalline defect density in the vicinity of the peak position Psof the hydrogen concentration is much lower than the crystalline defectdensity at the peak position Ks of the crystalline defect density. Thepeak position Ks of the crystalline defect density may be provided at aposition shallower than a range of the 1% full width centered on thepeak position Ps. The distance D between the peak position Ks of thecrystalline defect density and the peak position Ps of the hydrogenconcentration may be less than or equal to 40 μm or less than or equalto 20 μm. The distance D may be greater than or equal to 5 μm and lessthan or equal to 10 μm. The distance D may be greater than or equal tothe 1% full width of the hydrogen concentration. The distance D may begreater than or equal to the 1% full width of the net dopingconcentration at the position Ps. In this case, the 1% full width of thenet doping concentration is the width of the peak at 0.01 Np.

In the present example, the peak of the crystalline defect density isarranged at the position Kb that is between the position Pb2 and theposition Pb1. The crystalline defect density peak at the position Kbmainly includes crystalline defects formed when the hydrogen ions wereimplanted through the bottom surface 23 to the position Pb2. In thepresent example, crystalline defect density peaks are not providedanywhere other than the position Kb, farther on the bottom surface 23side than where the position Pb4 is located.

For example, hydrogen ions are implanted to the positions Pb4, Pb3, andPb1, and the semiconductor substrate 10 is annealed according to a firstcondition. In this way, hydrogen concentration distribution peaks areformed at the positions Pb4, Pb3, and Pb1. After this, hydrogen ions areimplanted to the position Ps and the position Pb2, and the semiconductorsubstrate 10 is annealed according to a second condition. The secondcondition may have a lower annealing temperature than the firstcondition. The crystalline defects generated by the hydrogen ionimplantation to the positions Pb4, Pb3, and Pb1 are mostly terminated bythe annealing at a relatively high temperature. In contrast to this,among the crystalline defects generated by the hydrogen ion implantationto the position Ps and the position Pb2, the crystalline defects in thevicinity of the position Ps and the position Pb2 are terminated by theannealing at a relatively low temperature. Since there is also a largeamount of hydrogen in the vicinity of the position Pb1, a large percentof the crystalline defects generated by the hydrogen ion implantation tothe position Pb2 are also terminated in the vicinity of the positionPb1. Therefore, the crystalline defect density has a peak between theposition Pb2 and the position Pb1.

In the present example, no hydrogen concentration peaks, other than thehydrogen concentration peak at the position Ps, are provided on the sidefrom which the hydrogen ions were implanted (the top surface 21 side inthe present example). On the other hand, in addition to the hydrogenconcentration peak at the position Pb2, another hydrogen concentrationpeak (position Pb1) is provided on the side from which the hydrogen ionswere implanted (the bottom surface 23 side in the present example). Theintegrated value of the crystalline defect density farther on the topsurface 21 side than where the position Ps is located may be greaterthan the integrated value of the crystalline defect density farther onthe bottom surface 23 side than where the position Pb2 is located.

The distribution drawing (D) shows the carrier lifetime distributionafter the hydrogen ions were implanted into the semiconductor substrate10 and annealing was then performed with prescribed conditions. Thecarrier lifetime distribution has a shape obtained by inverting thevertical axis of the crystalline defect density distribution. Thecarrier lifetime τ₀ may be the τ₀ described in the distribution diagram(D) of FIG. 3. For example, the position at which the carrier lifetimehas a minimum value matches the center peak position Ks of thecrystalline defect density. Furthermore, the position at which thecarrier lifetime is a local minimum value matches the center peak Kb ofthe crystalline defect density. In the same manner as in thedistribution drawing (D) of FIG. 3, in regions within ranges of FW1% Mcentered respectively on the hydrogen concentration peaks at thepositions Ps, Pb4, Pb3, Pb2, and Pb1, the carrier lifetime of thesemiconductor device 100 may be the maximum value τ₀.

The distribution drawing (E) shows the carrier mobility distributionafter the hydrogen ions were implanted into the semiconductor substrate10 and annealing was then performed with prescribed conditions. Thecarrier mobility μ₀ may be the μ₀ described in the distribution drawing(E) of FIG. 3. For example, the position at which the carrier mobilityhas a minimum value matches the center peak position Ks of thecrystalline defect density. Furthermore, the position at which thecarrier mobility is a local minimum value matches the center peak Kb ofthe crystalline defect density. In the same manner as in thedistribution drawing (E) of FIG. 3, in regions within ranges of FW1% Mcentered respectively on the hydrogen concentration peaks at thepositions Ps, Pb4, Pb3, Pb2, and Pb1, the carrier mobility of thesemiconductor device 100 may be the maximum value μ₀.

The distribution drawing (F) shows the carrier concentrationdistribution after the hydrogen ions were implanted into thesemiconductor substrate 10 and annealing was then performed withprescribed conditions. In the same manner as in the distribution drawing(F) of FIG. 3, the measured carrier concentration experiences an overalldrop in the region through which the hydrogen ions pass (the region fromthe bottom end of the anode region 14 of the semiconductor substrate 10to the vicinity of the position P). However, the region farther on thebottom surface 23 side than where the position Pb4 is located has anoverall high hydrogen concentration, and therefore the carrierconcentration is higher than the substrate concentration N₀.

In the semiconductor device 100 of the present example, the crystallinedefect density after annealing decreases around the hydrogenconcentration peak position Ps. Therefore, the carrier lifetime in thevicinity of the position Ps of the hydrogen concentration peakincreases, and becomes approximately τ₀.

FIG. 7B shows distributions of each of the net doping concentration (A),the hydrogen concentration and the helium concentration (B), thecrystalline defect density (C), the carrier lifetime (D), the carriermobility (E), and the carrier concentration (F), in a case where thecrystalline defect region 19-2 on the bottom surface 23 side is formedby implanting helium ions. Aside from the crystalline defect region 19-2on the bottom surface 23 side being formed by implanting helium ions,this example is the same as the example of FIG. 7A. The net dopingconcentration (A) and carrier concentration (F) distributions aresimilar to those in the example of FIG. 7A.

The distribution drawing (B) shows the chemical hydrogen concentrationand helium concentration distributions. The hydrogen concentrationdistribution is the same as the hydrogen concentration distribution inFIG. 7A. However, in the present example, there is a helium distributioninside the buffer region 20. In the present example, the heliumconcentration peak is arranged farther on the bottom surface 23 sidethan where the position Pb1 is located.

The helium concentration peak may be positioned between adjacenthydrogen concentration peaks. Specifically, the helium concentrationpeak may be positioned between Pb4 and Pb3, between Pb3 and Pb2, orbetween Pb2 and Pb1. As an example, the helium concentration peakindicated by the dashed line in the distribution drawing (B) ispositioned between Pb2 and Pb1. The helium may be introduced with one ofthe solid line distribution having a peak farther on the bottom surface23 side that where Pb1 is located and the dashed line distributionhaving a peak between Pb2 and Pb1, or may be introduced with both ofthese distributions.

The distribution drawing (C) shows the crystalline defect density afterthe hydrogen ions and helium ions were implanted into the semiconductorsubstrate 10 and annealing was then performed with prescribedconditions. The crystalline defect density in the crystalline defectregion 19-1 formed by implanting the hydrogen ions is the same as thecrystalline defect density in the crystalline defect region 19-1 in thedistribution drawing (C) of FIG. 7A. Furthermore, the crystalline defectregion 19-2 a indicated by the solid line in the distribution drawing(C) is a crystalline defect region in a case where helium ions have beenimplanted to the position indicated by the solid line in thedistribution diagram (B). The crystalline defect region 19-2 b is acrystalline defect region in a case where the helium ions have beenimplanted to the position indicated by the dashed line in thedistribution drawing (B). In the distribution drawings (D) and (E) aswell, the distributions corresponding to the crystalline defect region19-2 a are indicated by solid lines and the distributions correspondingto the crystalline defect region 19-2 b are indicated by dashed lines.The crystalline defect density distributions of the crystalline defectregions 19-2 a and 19-2 b formed by implanting helium ions have the sameshape as the helium concentration distributions. For example, the peakposition of the crystalline defect density matches the peak position ofthe helium concentration.

The distribution drawing (D) shows the carrier lifetime distributionafter the hydrogen ions and helium ions were implanted into thesemiconductor substrate 10 and annealing was then performed withprescribed conditions. The carrier lifetime distribution has a shapeobtained by inverting the vertical axis of the crystalline defectdensity distribution.

The distribution drawing (E) shows the carrier mobility distributionafter the hydrogen ions and helium ions were implanted into thesemiconductor substrate 10 and annealing was then performed withprescribed conditions.

In the semiconductor substrate 10, there is a large amount of hydrogenin the buffer region 20 and the region farther on the bottom surface 23side than where the buffer region 20 is located. Therefore, danglingbonds are easily terminated, and there are cases where it is difficultto form the crystalline defect region 19. In contrast to this, byforming the crystalline defect region 19-2 by implanting helium ions,which have a greater mass than hydrogen ions, it becomes easier forcrystalline defects such as vacancies and double vacancies to form. Inthis way, even when crystalline defects are terminated due to theannealing, it is possible for a certain density of crystalline defectsto remain in the buffer region 20 and farther on the bottom surface 23side than where the buffer region 20 is located. By providing thecrystalline defect region 19 in the buffer region 20 and the like, it ispossible to precisely control the tail current during the terminationperiod of switching, such as turn-off or reverse recovery, of thesemiconductor device 100, for example.

FIG. 7C shows distributions of each of the net doping concentration (A),the hydrogen concentration (B), the crystalline defect density (C), thecarrier lifetime (D), the carrier mobility (E), and the carrierconcentration (F) of another example. The vertical axis and horizontalaxis in each distribution drawing are the same as in the correspondingdistribution drawing in FIG. 3. In the present example, the crystallinedefect density (C), the carrier lifetime (D), the carrier mobility (E),and the carrier concentration (F) in the anode region 14 (a base region17 in which channels are formed in a transistor portion 70, describedfurther below) and the crystalline defect region 19-1 are different thanin the examples of FIGS. 7A and 7B. Each distribution at other positionsis the same as in the example of either FIG. 7A or 7B.

In the present example, the distributions of the crystalline defectdensity (C), the carrier lifetime (D), the carrier mobility (E), and thecarrier concentration (F) each have a peak in the crystalline defectregion 19-1. The crystalline defect density distribution peak has a tailSV1 farther on the top surface 21 side than where the center peakposition Ks is located and a tail SV2, which his steeper than the tailSV1, farther on the bottom surface 23 side than where the center peakposition Ks is located. The carrier lifetime distribution peak has atail Sτ1 farther on the top surface 21 side than where the center peakposition Ks is located and a tail Sτ2, which is steeper than the tailSτ1, farther on the bottom surface 23 side than where the center peakposition Ks is located. The carrier mobility distribution peak has atail Sμ1 farther on the top surface 21 side than where the center peakposition Ks is located and a tail Sμ2, which is steeper than the tailSμ1, farther on the bottom surface 23 side than where the center peakposition Ks is located. The carrier concentration distribution peak hasa tail SN1 farther on the top surface 21 side than where the center peakposition Ks is located and a tail SN2, which is steeper than the tailSN1, farther on the bottom surface 23 side than where the center peakposition Ks is located.

Each tail may be a portion in the corresponding distribution from theapex of the peak to where the value is the same as a prescribedreference value. This reference value may use the minimum value Nr₀ inthe drift region 18 for the crystalline defect density, the maximumvalue τ₀ in the drift region for the carrier lifetime, the maximum valueN₀ in the drift region 18 for the carrier mobility, and the minimumvalue N₀ in a portion from the hydrogen concentration peak position Psto the buffer region 20 for the carrier concentration. In thisspecification, “the same as” may include a case where the differencetherebetween is less than or equal to 10%.

None of the tails SV1, Sτ1, Sμ1, and SN1 of the present example reachthe anode region 14 (the base region 17 in the transistor portion 70).In other words, the crystalline defect density, the carrier lifetime,the carrier mobility, and the carrier concentration of the anode region14 and the base region 17 are the same as the reference values Nr₀, τ₀,μ₀, and N₀ described above. In this way, it is possible to reduce theeffect of forming the crystalline defects on the anode region 14 and thebase region 17. In particular, fluctuation of the gate threshold valueis restricted. The gate threshold value is determined by the position ofthe peak concentration of the base region 17. When the crystallinedefect density of the base region 17 at the peak position is higher thanNr₀, there are cases where the interface state or the like that affectsthe gate threshold value increases, and the gate threshold valuechanges. By causing the crystalline defect density of the base region 17at the peak position to be Nr₀, it is possible to minimize the effect onthe gate threshold value. By adjusting the hydrogen ion implantationposition and the annealing conditions after the hydrogen ionimplantation, for example, each tail can be restricted so as not toreach the anode region 14 and the base region 17.

FIG. 7D shows distributions of each of the net doping concentration (A),the hydrogen concentration (B), the crystalline defect density (C), thecarrier lifetime (D), the carrier mobility (E), and the carrierconcentration (F) of another example. The vertical axis and horizontalaxis in each distribution drawing are the same as in the correspondingdistribution drawing in FIG. 3. In the present example, the crystallinedefect density (C), the carrier lifetime (D), the carrier mobility (E),and the carrier concentration (F) in the anode region 14 (the baseregion 17 in the transistor portion 70) and the crystalline defectregion 19-1 are different than in the example of FIG. 7C. Eachdistribution at other positions is the same as in the example of FIG.7C.

In the present example, at least one of the tails SV1, Sτ1, Sμ1, and SN1reaches the anode region 14 or the base region 17. However, thecrystalline defect density, the carrier lifetime, the carrier mobility,and the carrier concentration of the anode region 14 and the base region17 are sufficiently close to the reference values Nr₀, τ₀, μ₀, and N₀described above.

In the present example, the crystalline defect density, the carrierlifetime, the carrier mobility, and the carrier concentration at thecenter peak position Ks are represented by Nrp, τp, μp, and Np.Furthermore, the crystalline defect density, the carrier lifetime, thecarrier mobility, and the carrier concentration in the anode region 14or base region 17 are represented by Nrb, τb, μb, and Nb. Thecrystalline defect density Nrb, the carrier lifetime τb, the carriermobility μb, and the carrier concentration Nb may be the values at aposition of the PN junction between the anode region 14 or base region17 and the N type region such as the drift region 18. For the carrierconcentration Nb, a local maximum value of the carrier concentration inthe N type region in contact with the PN junction may be used.

The crystalline defect density Nrb, the carrier lifetime τb, the carriermobility μb, and the carrier concentration Nb may be less than or equalto ½, less than or equal to ¼, less than or equal to 1/10, or less thanor equal to 1/100 of the corresponding crystalline defect density Nrp,the carrier lifetime τp, the carrier mobility τp, and the carrierconcentration Np at the center peak position Ks. In this way, it ispossible to reduce the effect of forming the crystalline defects on theanode region 14 and the base region 17.

FIG. 8A is a partial view of an example of a top surface of asemiconductor device 200 according to the present embodiment. Thesemiconductor device 200 of the present example is a semiconductor chipincluding a transistor portion 70 and a diode portion 80 providedadjacent to the transistor portion 70. The top surface of thesemiconductor device 200 may be the same as the top surface of thesemiconductor device 100 shown in FIG. 1A. The transistor portion 70includes a transistor such as an IGBT. The interface portion 90 is aregion of the transistor portion 70 adjacent to the diode portion 80.The diode portion 80 includes a diode such as an FWD (Free Wheel Diode)on the top surface of the semiconductor substrate 10. In FIG. 8A, thetop surface of the chip near the chip edge portion is shown, and otherregions are omitted.

Furthermore, in FIG. 8A the active region of the semiconductor substrate10 in the semiconductor device 200 is shown, but the semiconductordevice 200 may include an edge termination structure portion thatsurrounds the active region. The active region refers to a regionthrough which current flows when the semiconductor device 200 iscontrolled to be in the ON state. The edge termination structure portionrelaxes the electrical field concentration on the top surface 21 side ofthe semiconductor substrate 10. The edge termination structure portionhas a guard ring, a field plate, a RESURF, and a structure in whichthese components are combined, for example.

The semiconductor device 200 of the present example includes a gatetrench portion 40, the dummy trench portion 30, a well region 11, anemitter region 12, the base region 17, and the contact region 15 thatare provided within the semiconductor substrate 10 and exposed on thetop surface of the semiconductor substrate 10. Furthermore, thesemiconductor device 200 of the present example includes the emitterelectrode 52 and the gate metal layer 50 provided above the top surface21 of the semiconductor substrate 10. The emitter electrode 52 and thegate metal layer 50 are provided separated from each other.

An interlayer dielectric film is provided between the emitter electrode52 and gate metal layer 50 and the top surface 21 of the semiconductorsubstrate 10, but this interlayer dielectric film is omitted from FIG.8A. The interlayer dielectric film of the present example is providedwith a contact hole 56, a contact hole 49, and a contact hole 54 thatpenetrate through this interlayer dielectric film.

Furthermore, the emitter electrode 52 is connected to the dummyconducting portion within the dummy trench portion 30, via the contacthole 56. A connecting section 25 formed of a conductive material, suchas polysilicon doped with impurities, may be provided between theemitter electrode 52 and the dummy conducting portion. A dielectric suchas an oxide film is provided between the connecting section 25 and thetop surface 21 of the semiconductor substrate 10.

The gate metal layer 50 contacts the gate runner 48, via the contacthole 49. The gate runner 48 is formed of polysilicon or the like dopedwith impurities. The gate runner 48 is connected to a gate conductingportion inside the gate trench portion 40, on the top surface 21 of thesemiconductor substrate 10. The gate runner 48 is not connected to thedummy conducting portion within the dummy trench portion 30.

The gate runner 48 of the present example is formed from below thecontact hole 49 to a tip portion of the gate trench portion 40. Adielectric such as an oxide film is formed between the gate runner 48and the top surface 21 of the semiconductor substrate 10.

The gate conducting portion is exposed in the top surface 21 of thesemiconductor substrate 10, at the tip portion of the gate trenchportion 40. The gate trench portion 40 contacts the gate runner 48 atthe exposed portion of the gate conducting portion.

The emitter electrode 52 and the gate metal layer 50 are formed of amaterial including metal. At least a partial region of the emitterelectrode 52 may be formed by aluminum or an aluminum-silicon alloy.

At least a partial region of the gate metal layer 50 may be formed byaluminum or an aluminum-silicon alloy. The emitter electrode 52 and thegate metal layer 50 may include a barrier metal formed of titanium, atitanium compound, or the like, in an underlayer of the region formed ofaluminum or the like. Furthermore, the emitter electrode 52 and the gatemetal layer 50 may include a plug formed of tungsten or the like withinthe contact hole.

One or more gate trench portions 40 and one or more dummy trenchportions 30 are arranged at prescribed intervals along a prescribedarrangement direction (Y-axis direction in the present example). Thegate trench portion 40 may include two extending portions 39 that extendalong an extension direction (X-axis direction in the present example)perpendicular to the arrangement direction, which is parallel to the topsurface 21 of the semiconductor substrate 10, and a connecting portion41 that connects the two extending portions 39. At least part of theconnecting portion 41 is preferably formed to be U-shaped. By connectingthe end portions of the two extending portions 39 of the gate trenchportion 40, it is possible to relax the electrical field concentrationat the end portions of the extending portions 39. In this specification,there are cases where each extending portion 39 of the gate trenchportion 40 is treated as a single gate trench portion 40. The gaterunner 48 may be connected to the gate conducting portion at theconnecting portion 41 of the gate trench portion 40.

The dummy trench portion 30 of the present example may be U-shaped inthe top surface 21 of the semiconductor substrate 10, in the same manneras the gate trench portion 40. In other words, the dummy trench portion30 of the present example may include two extending portions 29 thatextend along the extension direction and a connecting portion 31 thatconnects the two extending portions 29.

The emitter electrode 52 is formed above the gate trench portion 40, thedummy trench portion 30, the well region 11, the emitter region 12, thebase region 17, and the contact region 15. The well region 11 has asecond conductivity type. The well region 11 is P+ type, for example.The well region 11 is formed in a predetermined range from an endportion of the active region on the side where the gate metal layer 50is provided. The diffusion depth of the well region 11 may be greaterthan the depth of the gate trench portion 40 and the dummy trenchportion 30. A region of parts of the gate trench portion 40 and thedummy trench portion 30 on the gate metal layer 50 side is formed in thewell region 11. Floors of the ends of the gate trench portion 40 and thedummy trench portion 30 in the extension direction may be covered by thewell region 11.

A mesa portion is provided adjacent to each trench portion in the Y-axisdirection, within a plane parallel to the top surface 21 of thesemiconductor substrate 10. The mesa portion is a portion of thesemiconductor substrate sandwiched between two adjacent trench portions.The mesa portion may be a portion from the top surface 21 of thesemiconductor substrate 10 to the depth of a deepest floor portion ofeach trench portion. A region sandwiched by extending portions of twoadjacent trench portions may be a mesa portion.

In the transistor portion 70, a first mesa portion 60 is providedadjacent to each trench portion. At the interface portion 90, which isthe portion of the transistor portion 70 forming an interface with thediode portion 80, a second mesa portion 62 is provided in a regionsandwiched by adjacent dummy trench portions 30. In the diode portion80, a third mesa portion 64 is provided in a region sandwiched byadjacent dummy trench portions 30.

A base region 17 of a second conductivity type is provided, in a mannerto be exposed in the top surface 21 of the semiconductor substrate 10,at both ends in the X-axis direction of each of the first mesa portion60, the second mesa portion 62, and the third mesa portion 64. The baseregion 17 of the present example is P− type, for example. FIG. 8A showsonly one end portion of the base region 17 in the X-axis direction.

The emitter region 12 is provided in contact with the gate trenchportion 40, on the top surface of the first mesa portion 60. The emitterregion 12 may be provided in the Y-axis direction, from one to the otherof two trench portions extending in the X-axis direction and sandwichingthe first mesa portion 60. The emitter region 12 is also provided belowthe contact hole 54.

The emitter region 12 may contact the dummy trench portion 30, but doesnot need to contact the dummy trench portion 30. In the present example,the emitter region 12 is provided in contact with the dummy trenchportion 30. The emitter region 12 of the present example is a firstconductivity type. The emitter region 12 of the present example is N+type, for example.

The contact region 15 of a second conductivity type, which has a higherdoping concentration than the base region 17, is provided on the topsurface of the first mesa portion 60. The contact region 15 of thepresent example is P+ type, for example. In the first mesa portion 60,the emitter region 12 and the contact region 15 may be provided in analternating manner in the extension direction of the gate trench portion40. The contact region 15 may be provided in the Y direction, from oneto the other of two trench portions extending in the X-axis directionand sandwiching the first mesa portion 60. The contact region 15 mayalso be provided below the contact hole 54.

The contact region 15 may contact the gate trench portion 40, but doesnot need to contact the gate trench portion 40. Furthermore, the contactregion 15 may contact the dummy trench portion 30, but does not need tocontact the dummy trench portion 30. In the present example, the contactregion 15 is provided in contact with the dummy trench portion 30 andthe gate trench portion 40.

The contact region 15 is provided on the top surface of the second mesaportion 62. The surface area of the contact region 15 provided on thetop surface of one second mesa portion 62 may be greater than thesurface area of the contact region 15 provided on the top surface of onefirst mesa portion 60. The surface area of the contact region 15provided on the top surface of one second mesa portion 62 may be greaterthan the surface area of the contact region 15 provided on the topsurface of one third mesa portion 64. On the second mesa portion 62, thecontact region 15 is also provided below the contact hole 54.

The contact region 15 on the top surface of the second mesa portion 62may be provided on the entire region sandwiched between the base regions17 provided at the respective end portions of the second mesa portion 62in the X-axis direction. With the second mesa portion 62, the carriersare more effectively withdrawn during turn-off, compared to the firstmesa portion 60.

The contact region 15 is provided on the top surface of the third mesaportion 64, at both end portions in the X-axis direction. Furthermore,at the top surface of the third mesa portion 64, the base region 17 isprovided in the region sandwiched by the contact regions 15 provided atthe respective end portions of the third mesa portion 64 in the X-axisdirection. The base region 17 may be provided on the entire regionsandwiched by these contact regions 15 in the X-axis direction. On thethird mesa portion 64, the base region 17 may also be provided below thecontact hole 54. The contact region 15 may also be provided below thecontact hole 54.

On the third mesa portion 64, the contact region 15 and the base region17 are formed from one of the dummy trench portions 30 sandwiching thethird mesa portion 64 to the other dummy trench portion 30. In otherwords, on the top surface of the semiconductor substrate, the width ofthe third mesa portion 64 in the Y-axis direction and the width of thecontact region 15 or the base region 17 in the Y-axis direction providedon this third mesa portion 64 are equal.

The emitter region 12 may be formed, but does not need to be formed, onthe third mesa portion 64. In the present example, the emitter region 12is not formed on the third mesa portion 64.

In the semiconductor device 200 of the present example, the dummy trenchportion 30 is formed in the diode portion 80. The linear extendingportions 29 of respective adjacent dummy trench portions 30 may beconnected to each other by a connecting portion 31. The third mesaportion 64 is a region sandwiched by the respective dummy trenchportions 30.

The diode portion 80 includes the cathode region 82 of a firstconductivity type, on the bottom surface 23 side of the semiconductorsubstrate 10. The cathode region 82 of the present example is N+ type,for example. In FIG. 8A, the region where the cathode region 82 isprovided, in the top surface view of the semiconductor substrate 10, isindicated by a single-dot chain line. The diode portion 80 may be aregion where the cathode region 82 is projected onto the top surface 21of the semiconductor substrate 10. Furthermore, the entirety of thethird mesa portion 64 where a portion of the cathode region 82 isprovided and the dummy trench portions 30 adjacent to this third mesaportion 64 may be included in the diode portion 80. The region where thecathode region 82 is projected into the top surface 21 of thesemiconductor substrate 10 may be distanced from the contact region 15in the positive X-axis direction.

A collector region of a second conductivity type may be formed in aregion where the cathode region 82 is not formed on the bottom surface23 of the semiconductor substrate 10. The collector region of thepresent example is P+ type, for example. The collector region may beformed at a position on the diode portion 80 where the end portion ofthe contact hole 54 on the negative X-axis direction side is projectedonto the bottom surface 23 of the semiconductor substrate 10.

In the portion of the transistor portion 70 excluding the interfaceportion 90, the contact hole 54 is formed above each region of thecontact region 15 and the emitter region 12. In each first mesa portion60, excluding the first mesa portions 60 adjacent to the interfaceportion 90, the contact hole 54 is provided in a manner to not overlapwith the gate trench portion 40 and the dummy trench portion 30extending in the X-axis direction, in the top surface view of FIG. 8A.The width of the contact hole 54 in the Y-axis direction may be lessthan the widths of the emitter region 12 and the contact region 15 inthe Y-axis direction.

In the portion of the transistor portion 70 excluding the interfaceportion 90, each contact hole 54 is provided continuously from above thecontact region 15 provided farthest on the negative X-axis directionside of a first mesa portion 60 to above the contact region 15 providedfarthest on the negative X-axis direction side of the first mesa portion60, in the top surface view of the semiconductor substrate 10semiconductor substrate 10 shown in FIG. 8A. The contact hole 54 may beprovided in a manner to not overlap with at least a portion of thecontact region 15 provided farthest on the negative X-axis directionside of the first mesa portion 60, in the top surface view of thesemiconductor substrate 10 shown in FIG. 8A. The contact hole 54 may beprovided in a manner to not overlap with at least a portion of thecontact region 15 provided farthest on the positive X-axis directionside of the first mesa portion 60, in the top surface view of thesemiconductor substrate 10 shown in FIG. 8A.

In the interface portion 90, the contact hole 54 is formed above thecontact region 15. In the second mesa portion 62, the contact hole 54may be formed in a manner to not overlap with the dummy trench portion30 extending in the X-axis direction, in the top surface view of thesemiconductor substrate 10 shown in FIG. 8A. The width of the contacthole 54 in the Y-axis direction may be less than the width of thecontact region 15 in the Y-axis direction.

In the interface portion 90, the contact hole 54 may be providedcontinuously in the X-axis direction to a region above the contactregion 15 provided to the second mesa portion 62, in the top surfaceview shown in FIG. 8A. The contact hole 54 may be provided in a mannerto overlap with at least a portion of the contact region 15 provided onthe second mesa portion 62, in the top surface view of FIG. 8A.

In the diode portion 80, the contact hole 54 is formed above the baseregion 17 and the contact region 15. In the third mesa portion 64, thecontact hole 54 may be provided in a manner to not overlap with thedummy trench portion 30 extending in the X-axis direction, in the topsurface view shown in FIG. 8A. The width of the contact hole 54 in theY-axis direction may be less than the widths of the base region 17 andthe contact region 15 in the Y-axis direction.

In the diode portion 80, the contact hole 54 may be providedcontinuously from above the contact region 15 provided farthest on thenegative X-axis direction side of the third mesa portion 64 to above thecontact region 15 provided farthest on the positive X-axis directionside of the third mesa portion 64, in the top surface view shown in FIG.8A. The contact hole 54 may be provided in a manner to overlap with atleast a portion of the contact region 15 provided farthest on thenegative X-axis direction side of the third mesa portion 64, in the topsurface view shown in FIG. 8A. The contact hole 54 may be provided in amanner to overlap with at least a portion of the contact region 15provided farthest on the positive X-axis direction side of the thirdmesa portion 64, in the top surface view shown in FIG. 8A.

In the transistor portion 70, the accumulation region 16 of a firstconductivity type may be provided below the base region 17. Theaccumulation region 16 of the present example is N+ type, for example.In FIG. 8A, the ranges in which the accumulation region 16 is formed areindicated by dashed lines. The accumulation region 16 may be formed froma region where the contact region 15 on the −X-axis direction endoverlaps with a contact hole 54 to the +X-axis direction, in the topsurface view of the semiconductor substrate. The accumulation region 16may be provided, but does not need to be provided, in the diode portion80.

The semiconductor device 200 of the present example includes acrystalline defect region 19 inside the semiconductor substrate 10. Asshown in FIGS. 1A to 6, the semiconductor device 200 may include one ofthe crystalline defect region 19-1 on the top surface 21 side and thecrystalline defect region 19-2 on the bottom surface 23 side, or mayinclude both of these crystalline defect regions. The semiconductordevice 200 of the present invention includes both of the crystallinedefect regions 19-1 and 19-2. The crystalline defect region 19-2 may beprovided to all of the transistor portion 70 and all of the diodeportion 80. The crystalline defect region 19-1 may be provided to all ofthe diode portion 80 and a portion of the transistor portion 70.

In FIG. 8A, the region where the crystalline defect region 19-1 isprovided is indicated by a single-dot chain line and arrow symbols. Inthe present example, the crystalline defect region 19-1 is arranged in aregion where none of the diode portion 80 in the XY-plane overlaps witha gate trench portion 40 in the transistor portion 70. The crystallinedefect region 19-1 may be provided continuously in the Y-axis directionfrom the diode portion 80 to the first mesa portion 60 in contact withthe gate trench portion 40 closest to the diode portion 80 in thetransistor portion 70. In another example, the crystalline defect region19-1 may be arranged discretely in the Y-direction, so as not to overlapwith any gate trench portions 40 in the transistor portion 70.

FIG. 8B is a partial view of another example of a top surface of thesemiconductor device 200. In the semiconductor device 200 of the presentexample, the arrangement of the crystalline defect region 19-1 isdifferent from the arrangement in the example of FIG. 8A. Otherstructures are the same as in the example of FIG. 8A.

In the semiconductor device 200 of the present example, the crystallinedefect region 19-1 is arranged overlapping with a gate trench portion 40of the transistor portion 70. More specifically, the crystalline defectregion 19-1 is arranged overlapping with one or more gate trenchportions 40 arranged closest to the diode portion 80, among the gatetrench portions 40 of the transistor portion 70. The crystalline defectregion 19-1 may be arranged in a manner to not overlap with at least thefirst mesa portion 60 arranged in the center in the Y-axis direction, ineach gate trench portion 40 of the transistor portion 70.

FIG. 8C is a partial view of another example of a top surface of thesemiconductor device 200. In the semiconductor device 200 of the presentexample, the arrangement of the crystalline defect region 19-1 and thecathode region 82 is different from the arrangement in the example ofFIG. 8A. The other structures are the same as in the example of FIG. 8A.

The crystalline defect region 19-1 may be provided in a wider range thanthe cathode region 82 in the X-axis direction and the Y-axis direction.In FIG. 8C, the crystalline defect region 19-1 is arranged in theinterface portion 90 and the diode portion 80 but is not arranged in theportion of the transistor portion 70 that is not the interface portion90, in the Y-axis direction. The surface area of the contact region 15exposed in the top surface of one second mesa portion 62 of theinterface portion 90 is greater than the surface area of the contactregion 15 exposed in the top surface of one first mesa portion 60 in thetransistor portion 70. The second mesa portion 62 may have aconfiguration obtained by replacing the emitter region 12 in the firstmesa portion 60 with the contact region 15. The cathode region 82 isprovided in at least a portion of the diode portion 80 in the Y-axisdirection. In the present example, the region sandwiched by transistorportions 70 in the Y-axis direction is the diode portion 80. The cathoderegion 82 of FIG. 8C is not provided in one or more of the third mesaportions 64 closest to the interface portion 90 in the diode portion 80.The cathode region 82 of FIG. 8C is provided distanced in the X-axisdirection from the contact region 15 in the diode portion 80.

An end portion of the crystalline defect region 19-1 in the X-axisdirection is arranged between an end portion of the cathode region 82 inthe X-axis direction and the gate metal layer 50. The end portion of thecrystalline defect region 19-1 in the X-axis direction may be arrangedbetween the contact hole 54 and the gate metal layer 50 (the crystallinedefect region 19-1 a in FIG. 8C). In another example, the end portion ofthe crystalline defect region 19-1 in the X-axis direction may bearranged between the dummy trench portion 30 and the gate metal layer 50(the crystalline defect region 19-1 b in FIG. 8C).

The end portion of the crystalline defect region 19-1 in the X-axisdirection may be arranged inside the well region 11, in the top surfaceview (the crystalline defect region 19-1 b in FIG. 8C). The P type wellregion 11 has a higher doping concentration than the P type anode region14 or base region 17. By providing the crystalline defect region 19-1 inthe well region 11 as well, it is possible to restrict the implantationof holes from the well region 11 toward the cathode region 82.

An end portion of the crystalline defect region 19-1 in the Y-axisdirection may be arranged in a dummy trench portion 30 or a first mesaportion 60 farther on the diode portion 80 side than where the gatetrench portion 40 provided farthest on the diode portion 80 side, amongthe gate trench portions 40 of the transistor portion 70, is located(the crystalline defect region 19-1 c in FIG. 8C). In this way, it ispossible to restrict the implantation of holes from the transistorportion 70 toward the cathode region 82, without affecting the gatethreshold value.

The crystalline defect region 19-1 may extend to the gate runner 48 orthe gate metal layer 50 in the Y-axis direction. The end portion of thecrystalline defect region 19-1 in the Y-axis direction may reach thegate runner 48, reach the gate metal layer 50, or be positioned toextend beyond the gate metal layer 50. In this way, the carriersremaining in the gate runner 48 or the gate metal layer 50 can bereduced, and the effect on the switching operation can be restricted.

A gate dielectric is formed on the bottom surface 23 side of the gaterunner 48 or gate metal layer 50, but this is also a region where aninversion layer channel is not formed. During the ion implantation forforming the crystalline defect region 19-1, the implanted ions are alsointroduced into or pass through the gate dielectric on the bottomsurface 23 side of the gate runner 48 or gate metal layer 50. Therefore,there are cases where damage is formed in the gate dielectric as well,during the ion implantation. However, since the inversion layer channelis not formed on the bottom surface 23 side of the gate runner 48 orgate metal layer 50, the effect on the gate threshold value issufficiently small.

The contact region 15 in the top surface of the second mesa portion 62does not need to be provided in the entire region sandwiched by the baseregions 17 provided at the respective end portions of the second mesaportion 62 in the X-axis direction. Specifically, the contact regions 15in the top surface of the second mesa portion 62 cover only both ends ofthe contact hole 54, and the base region 17 may be exposed in the topsurface of the second mesa portion 62 sandwiched by these contactregions 15. In the top surface of the second mesa portion 62, thisexposed surface area of the base region 17 may be greater than, or 10times or more greater than, the surface are of the contact regions 15that cover both ends of the contact hole 54. Furthermore, theconfiguration may be the same as that of the diode portion 80.

FIG. 8D is a partial view of another example of a top surface of thesemiconductor device 200. In the semiconductor device 200 of the presentexample, the arrangement of the cathode region 82 in the Y-axisdirection is different from the arrangement in the example of FIG. 8C.The other structures are the same as in the example of FIG. 8C. Theposition of an end portion of the crystalline defect region 19-1 in theY-axis direction may be the same as in the example of FIG. 8C.

The cathode region 82 of the present example is provided in the entiretyof the diode portion 80 in the Y-axis direction. Furthermore, in theY-axis direction, the crystalline defect region 19-1 is provided in apartial region of the transistor portion 70 in contact with the diodeportion 80. The crystalline defect region 19-1 is also provided to thefirst mesa portions 60 outside the interface portion 90. However, thecrystalline defect region 19-1 is not provided in a prescribed rangethat includes the center of the transistor portion 70 in the Y-axisdirection. With such a configuration, it is possible to restrict theflow of carriers from the cathode region 82 to the top surface side ofthe transistor portion 70.

FIG. 9A shows an example of the d-d′ cross section in FIG. 8A. The d-d′cross section is a YZ-plane that passes through the emitter region 12and the contact region 15 in the transistor portion 70 and the diodeportion 80. The semiconductor device 200 of the present example includesthe semiconductor substrate 10, the interlayer dielectric film 38, theemitter electrode 52, and the collector electrode 24, in the d-d′ crosssection. The emitter electrode 52 is provided on the top surface 21 ofthe semiconductor substrate 10 and the top surface of the interlayerdielectric film 38.

The region A corresponds to the semiconductor device 100 shown in FIG.5. However, in the semiconductor device 100 shown in FIG. 5, the dummytrench portions 30 and the interlayer dielectric film 38 of FIG. 9A arenot provided. Furthermore, the emitter electrode 52 in FIG. 9Acorresponds to the top-surface-side electrode 53 in FIG. 5.

The collector electrode 24 is provided on the bottom surface 23 of thesemiconductor substrate 10. The emitter electrode 52 and the collectorelectrode 24 are formed of a conductive material such as metal.

The semiconductor substrate 10 may be a silicon substrate, a siliconcarbide substrate, or a nitride semiconductor substrate such as agallium nitride substrate. The semiconductor substrate 10 of the presentexample is a silicon substrate.

The semiconductor substrate 10 includes the drift region 18 of a firstconductivity type. The drift region 18 of the present example is N−type. The drift region 18 may be a remaining region in the semiconductorsubstrate 10 where no other doping region is provided.

One or more gate trench portions 40 and one or more dummy trenchportions 30 are provided on the top surface 21 of the semiconductorsubstrate 10. Each trench portion is provided from the top surface 21,penetrates through the base region 17, and reaches the drift region 18.

The gate trench portion 40 includes a gate trench provided in the topsurface 21, as well as a gate dielectric 42 and a gate conductingportion 44 provided within the gate trench. The gate dielectric 42 isprovided covering an inner wall of the gate trench. The gate dielectric42 may be formed by oxidizing or nitriding the semiconductor of theinner wall of the gate trench. The gate conducting portion 44 isprovided farther inward than the gate dielectric 42 inside the gatetrench. In other words, the gate dielectric 42 insulates the gateconducting portion 44 and the semiconductor substrate 10 from eachother. The gate conducting portion 44 is formed of a conductive materialsuch as polysilicon.

The gate conducting portion 44 is provided surrounded by the gatedielectric 42, inside the gate trench portion 40. The gate conductingportion 44 includes a region that, in the depth direction, sandwichesthe gate dielectric 42 and is opposite at least the adjacent base region17. The gate trench portion 40 in this cross section is covered by theinterlayer dielectric film 38 on the top surface 21. When a prescribedvoltage is applied to the gate conducting portion 44, a channel isformed by the electron inversion layer in the surface layer of theinterface surface where the base region 17 contacts the gate trench.

The dummy trench portion 30 may have the same structure as the gatetrench portion 40, in this cross section. The dummy trench portion 30includes a dummy trench provided on the top surface 21 side, as well asa dummy dielectric 32 and a dummy conducting portion 34 provided insidethe dummy trench. The top end of the dummy trench may be at the sameposition as the top surface 21 in the Z-axis direction. The dummydielectric 32 is provided covering the inner wall of the dummy trench.The dummy conducting portion 34 is provided surrounded by the dummydielectric 32, inside the dummy trench portion 30. The dummy dielectric32 insulates the dummy conducting portion 34 and the semiconductorsubstrate 10 from each other.

The dummy conducting portion 34 may be formed of the same material asthe gate conducting portion 44. For example, the dummy conductingportion 34 is formed of a conductive material such as polysilicon. Thedummy conducting portion 34 may have the same length as the gateconducting portion 44 in the depth direction. The floor portions of thedummy trench portion 30 and the gate trench portion 40 may be curvedsurfaces (curved shapes in the cross section) that bulge downward.

In the first mesa portion 60, the accumulation region 16 is provide incontact with the gate trench portion 40, above the drift region 18. In acase where a plurality of accumulation regions 16 are provided, therespective accumulation regions 16 are arranged along the Z-axisdirection. The accumulation region 16 is N+ type, for example. Thedoping concentration of the accumulation region 16 is higher than thedoping concentration of the drift region 18, and the dopant isaccumulated in the accumulation region 16 with a higher concentrationthan in the drift region 18. By providing the accumulation region 16, itis possible to increase the carrier implantation enhancement effect (IEeffect) and reduce the ON voltage.

In the first mesa portion 60, the accumulation region 16 may be incontact with the dummy trench portion 30 or separated from the dummytrench portion 30. FIG. 9A shows an example in which the accumulationregion 16 is provided in contact with the dummy trench portion 30.

In the first mesa portion 60, the base region 17 of a secondconductivity type is provided in contact with the gate trench portion40, above the accumulation region 16. The base region 17 is N− type, forexample. In the first mesa portion 60, the base region 17 may beprovided in contact with the dummy trench portion 30.

In the second mesa portion 62 of the interface portion 90, the baseregion 17 of a second conductivity type is provided in contact with thedummy trench portion 30, above the drift region 18. In the third mesaportion 64 of the diode portion 80, the anode region 14 of a secondconductivity type is provided in contact with the dummy trench portion30, above the drift region 18. The anode region 14 is provided incontact with the top surface 21.

In the first mesa portion 60, the emitter region 12 is provided incontact with the top surface 21 and in contact with the gate trenchportion 40, in the d-d′ cross section. The doping concentration of theemitter region 12 is higher than the doping concentration of the driftregion 18. In the first mesa portion 60, the contact region 15 isprovided in contact with the top surface 21 and in contact with the gatetrench portion 40, on the positive and negative X-direction sides inthis d-d′ cross section.

In the second mesa portion 62, the contact region 15 is provided incontact with the dummy trench portion 30 on the top surface 21. Thecontact region 15 may be in contact with the dummy trench portion 30 orseparated from the dummy trench portion 30. FIG. 9A shows an example inwhich the contact region 15 is provided in contact with the dummy trenchportion 30.

In the transistor portion 70, the collector region 22 of a secondconductivity type is provided below the drift region 18. The collectorregion 22 of the present example is P+ type, for example. The collectorregion 22 is provided in contact with the bottom surface 23. In thediode portion 80, the cathode region 82 of a first conductivity type,with a higher doping concentration than the drift region 18, is providedbelow the drift region 18. The cathode region 82 of the present exampleis N+ type, for example. The cathode region 82 is provided in contactwith the bottom surface 23.

In the semiconductor device 200 of the present example, thesemiconductor substrate 10 may include the buffer region 20 of a firstconductivity type, with a higher doping concentration than the driftregion 18, between the drift region 18 and the bottom surface 23 of thesemiconductor substrate 10. The buffer region 20 is provided to includea first position Ps′. The buffer region of the present example is N+type, for example. In the present example, the buffer region 20 isprovided in contact with the drift region 18.

In the semiconductor device 200 of the present example, a regionincluding hydrogen is provided inside the semiconductor substrate 10. Inthe semiconductor device 200 of the present example, the hydrogenconcentration distribution in the depth direction of the semiconductorsubstrate 10 has a concentration distribution peak at a first positionPs, which is a predetermined distance Dps in the depth direction of thesemiconductor substrate 10 away from one main surface of thesemiconductor substrate 10, i.e. the top surface 21.

In FIG. 9A, the hydrogen concentration distribution peak at the firstposition Ps is indicated by the symbol (marker) “x”. The first positionPs is arranged farther on the top surface 21 side than where ½ thethickness of the semiconductor substrate 10 is located. Thesemiconductor substrate 10 is provided with the high concentrationregion 26, as a region including the hydrogen implanted to the firstposition Ps. The high concentration region 26 is provided in the samerange as the crystalline defect region 19-1 shown in FIG. 8A, in theXY-plane. In other words, in the XY plane, the high concentration region26 is provided in the entire diode portion 80 and at least a region ofthe transistor portion 70 that does not overlap with the gate trenchportion 40.

In the semiconductor device 200 of the present example, the hydrogenconcentration distribution has peaks at a plurality of positions in thebuffer region 20. Specifically, there are concentration distributionpeaks at four locations that are a position Pb4, a position Pb3, aposition Pb2, and a position Pb1, in order from the top surface sidetoward the bottom surface side of the buffer region 20. In FIG. 9A, thepeaks of the hydrogen concentration distribution at the plurality ofpositions in the Z-axis direction are indicated by the symbol (marker)“x”.

The buffer region 20 of the present example may be a region formed byannealing the hydrogen that has been implanted through the bottomsurface 23 into the semiconductor substrate 10 at the position Pb4, theposition Pb3, the position Pb2, and the position Pb1. By annealing thesemiconductor substrate 10 into which the hydrogen has been implanted,the hydrogen is activated as a donor, and the buffer region 20 with thehigher doping concentration than the drift region 18 is formed. Theformation of the buffer region 20 is described further below.

The first position Ps may be the doping concentration peak position ofthe high concentration region 26 after the annealing of thesemiconductor substrate 10 into which the hydrogen has been implanted.After the annealing, the doping concentration at the first position Psmay be greater than or equal to 1×10¹⁴ (/cm³) and less than or equal to1×10¹⁵ (/cm³).

In the semiconductor device 200 of the present example, the bufferregion 20 has a higher doping concentration than the drift region 18.Therefore, the buffer region 20 can function as a field stop region thatprevents the depletion layer, which spreads from the bottom surface sideof the anode region 14 and the base region 17, from reaching the cathoderegion 82 and the collector region 22.

The semiconductor device 200 of the present example is provided with thecrystalline defect regions 19-1 and 19-2. As shown in FIG. 8A, thecrystalline defect region 19-1 is provided in the entire diode portion80 and at least a portion of the region of the transistor portion 70that does not overlap with the gate trench portion 40. The crystallinedefect region 19-2 may be provided in the entire diode portion 80 andthe entire transistor portion 70, in the XY-plane.

FIG. 9B shows an example of the d-d′ cross section in FIG. 8B. Thesemiconductor device 200 of the present example differs from thesemiconductor device 200 shown in FIG. 9A in terms of the range in whichthe crystalline defect region 19-1 and the high concentration region 26are provided in the XY-plan. The other structures are the same as in theexample shown in FIG. 9A.

In the present embodiment, the crystalline defect region 19-1 and thehigh concentration region 26 are provided in the entire diode portion 80and a portion of the transistor portion 70, in the XY plane. In thetransistor portion 70, the crystalline defect region 19-1 and the highconcentration region 26 are provided in a region that is in contact withthe diode portion 80 and overlaps with one or more gate trench portions40.

FIG. 9C shows an example of the d-d′ cross section in FIG. 8B. Thesemiconductor device 200 of the present example differs from thesemiconductor device 200 shown in FIG. 9A in terms of the range in whichthe crystalline defect region 19-1 c and the high concentration region26 are provided in the XY-plan, and in terms of the interface positionbetween the collector region 22 and the cathode region 82. The otherstructures are the same as in the example shown in FIG. 9A.

FIG. 10A shows an example of an outline of a semiconductor devicemanufacturing method according to the present embodiment. In the presentexample, the crystalline defect region 19-1 on the top surface 21 sideis formed by implanting hydrogen ions (protons in the present example)and the crystalline defect region 19-2 on the bottom surface 23 side isformed by implanting helium ions. As shown in FIG. 10A, in thesemiconductor device manufacturing method, before the protonimplantation in step S1006 and onward, the ion implantation into thebottom surface 23 in step S1002 and laser annealing of the bottomsurface 23 in step S1004 are performed, for example.

The ions implanted into the bottom surface 23 in step S1002 are B(boron) and P (phosphorus), for example. In step S1002, using boron andphosphorus as an example, these elements are implanted respectively intothe region to be P type and the region to be N type in the bottomsurface 23.

In step S1004, laser annealing is performed on the boron and phosphorusimplanted in step S1002. Due to step S1004, the collector region 22 isformed in the region where boron was implanted and the cathode region 82is formed in the region where phosphorus was implanted.

Next, in step S1006, protons are implanted through the bottom surface23. The proton implantation of step S1006 is performed a plurality oftimes, as shown by step S1006-1, step S1006-2, step S1006-3, and stepS1006-4. The present example shows an example in which protonimplantation is performed four times in step S1006. In step S1006,protons are implanted into the region where the buffer region 20 is tobe formed.

In step S1008, the semiconductor substrate 10 into which the protonshave been implanted is annealed at a second temperature. In the presentexample, the second temperature may be greater than or equal to 330° C.and less than or equal to 450° C., and may be 370° C. for example.Furthermore, the second temperature may be greater than or equal to 350°C. and less than or equal to 420° C. or may be greater than or equal to370° C. and less than or equal to 400° C. The annealing time in stepS1008 may be greater than or equal to 30 minutes and less than or equalto 10 hours, and is 5 hours in the present example. Furthermore, theannealing time in step S1008 may be greater than or equal to 1 hour andless than or equal to 7 hours.

Next, in step S1010, helium ions are implanted through the bottomsurface 23. Furthermore, protons are implanted through the top surface21. The helium ions are implanted to a depth at which the defect densitypeak of the crystalline defect region 19-2 is to be formed. The protonsare implanted to a position deeper than the region in which the defectdensity peak of the crystalline defect region 19-1 is to be formed. Theprotons may be implanted to a depth at which the high concentrationregion 26 is to be formed. Either the helium ion implantation or theproton implantation may be performed first.

In step S1012, the semiconductor substrate 10 into which the protons andhelium ions have been implanted is annealed at a first temperature. Thefirst temperature is lower than the second temperature. In the presentexample, the first temperature may be 360° C.

The first temperature in step S1012 may be a temperature that causes thehydrogen to terminate the dangling bonds included in the vacancies anddouble vacancies, at and near (e.g. the FW1% region) the peak positionPs of the hydrogen ions implanted in step S1010. The first temperaturemay be greater than or equal to 300° C. and less than or equal to 420°C., for example, and is 360° C. in the present example. Furthermore, thefirst temperature may be greater than or equal to 330° C. and less thanor equal to 400° C. or may be greater than or equal to 350° C. and lessthan or equal to 380° C. Yet further, the first temperature may be lessthan 370° C., or may be less than or equal to 360° C.

The annealing time in step 1012 may be shorter than the annealing timein step S1008. The annealing time in step S1012 may be greater than orequal to 30 minutes and less than or equal to 8 hours, and is 1 hour inthe present example. Furthermore, the annealing time in step S1012 maybe greater than or equal to 1 hour and less than or equal to 5 hours. Bycausing at least one of the annealing temperature and the annealing timein step S1012 to be less than the annealing temperature or the annealingtime in step S1008, it becomes easy for the crystalline defectsgenerated by implanting the protons and helium ions to remain. With sucha process, it is possible to form the semiconductor device such as shownin FIG. 7B.

Furthermore, after step S1012, a step (not shown in the drawing) offorming an electrode on the bottom surface 23 may be performed. Thiselectrode formation step includes one or more steps of depositing ametal film. After this metal film deposition step, an electrodeannealing step may be performed. The temperature in the electrodeannealing step is lower than the first temperature. For example, thetemperature in the electrode annealing step may be greater than or equalto 140° C. and less than or equal to 330° C. The temperature in theelectrode annealing step may be greater than or equal to 220° C.

There are cases where the semiconductor device is soldered to a circuitboard such as a DCB (Direct Copper Bond) substrate after thesemiconductor substrate is formed into chips by dicing. The solderingtemperature at this time is a third temperature. The first temperatureof the annealing in step S1012 is higher than the third temperatureduring the soldering. For example, the soldering temperature may begreater than or equal to 280° C. and less than or equal to 400 C. Aslong as the third temperature is lower than the first temperature, thethird temperature may be lower than, equal to, or higher than thetemperature in the electrode annealing step.

The soldering time may be greater than or equal to 100 seconds and lessthan or equal to 500 seconds. The annealing time in step S1012 may belonger than the soldering time. Due to such conditions, it is possibleto terminate the crystalline defects with the hydrogen during thesoldering. The annealing time in step S1012 may be greater than or equalto 10 minutes or may be greater than or equal to 30 minutes. Thisannealing time may be less than or equal to 2 hours or less than orequal to 1 hour. Based on the above, with the second temperature beingT2, the first temperature being T1, and the third temperature being T3,it is preferable that T2>T1>T3.

FIG. 10B shows another example of the semiconductor device manufacturingmethod. In the present example, the crystalline defect region 19-1 onthe top surface 21 side and the crystalline defect region 19-2 on thebottom surface 23 side are formed by proton implantation. Step S1002 andstep S1004 of the present example are the same as S1002 and S1004 shownin FIG. 10A.

In step S1006, protons are implanted through the bottom surface 23. Theproton implantation of step S1006 may be performed a plurality of times,as shown by step S1006-1, step S1006-2, and step S1006-3. In step S1006,the protons are implanted to the positions of all but one of theplurality of hydrogen peaks to be formed in the buffer region 20. Thepresent example shows an example in which the proton implantation isperformed three times in step S1006.

In step S1008, the semiconductor substrate 10 into which the protonshave been implanted is annealed at a second temperature. In the presentexample, the second temperature may be 370° C. The annealing time may be5 hours.

Next, at step S1011, the protons are implanted through the top surface21 and the bottom surface 23. The protons implanted through the bottomsurface 23 are implanted to the position of the hydrogen peak whereprotons were not implanted in step S1006, among the plurality hydrogenpeaks to be formed in the buffer region 20. The protons implantedthrough the top surface 21 are implanted to a position deeper than theregion where the defect density peak of the crystalline defect region19-1 is to be formed. Either the proton implantation through the topsurface 21 or the proton implantation through the bottom surface 23 maybe performed first.

In step S1012, the semiconductor substrate 10 into which the protons andhelium ions have been implanted is annealed at the first temperature.Step S1012 is the same as step S1012 shown in FIG. 10A. Thesemiconductor device such as shown in FIG. 7A can be formed by such aprocess.

FIG. 11 shows another example of the semiconductor device manufacturingmethod according to the present embodiment. FIG. 11 shows the details ofstep S1010 and step S1012 shown in FIG. 10A. As shown in FIG. 11, instep S1010, the protons are implanted in the depth direction of thesemiconductor substrate 10, through one main surface of thesemiconductor substrate 10, i.e. the top surface 21. In the presentexample, the protons are implanted in the depth direction of thesemiconductor substrate 10 to the depth of the first position Ps that isthe distance Dps away from the top surface 21. In FIG. 11, the protonsimplanted to the depth of the first position Ps are indicated by “x”. Instep S1010, the proton implantation amount may be greater than or equalto 1×10¹² (/cm²) and less than or equal to 1×10¹³ (/cm²).

Due to the proton implantation from the top surface 21, crystallinedefects are generated from the top surface 21 of the semiconductorsubstrate 10 to the first position Ps. Furthermore, due to the protonimplantation from the top surface 21, the hydrogen concentration forms adistribution in the depth direction of the semiconductor substrate 10with the first position Ps as a peak. Yet further, in step S1010, thehelium ions are implanted in the depth direction of the semiconductorsubstrate 10 from the bottom surface 23. In the present example, thehelium ions are implanted to the position Kb.

Next, in step S1012, the semiconductor substrate 10 into which theprotons and helium ions have been implanted is annealed at the firsttemperature. The first temperature may be 360° C. The annealing time maybe 1 hour. Due to step S1012, the crystalline defects generated by theimplantation of the protons and helium ions are terminated by thehydrogen. In this way, the crystalline defect density peaks are formedat the position Ks and the position Kb. Furthermore, due to thisannealing, the hydrogen implanted to the first position Ps is activatedas a donor.

The semiconductor device of the present example uses, as thetop-surface-side lifetime control region 74, the crystalline defectregion 19-1 which ranges in the depth direction of the semiconductordevice with the position Ks as the concentration distribution peak.Furthermore, the semiconductor device of the present example uses, asthe high concentration region 26, the region that includes the firstposition Ps and in which the hydrogen has been activated as a donor.

FIG. 12 shows distributions of each of the hydrogen concentration (B),the crystalline defect density (C), and the carrier concentration (F),along the h-h′ line in FIG. 11. In FIG. 12, the distributions before theannealing in step S1010 of FIG. 11 are indicated by dashed lines, andthe distributions after the annealing in step S1012 are shown by solidlines.

As shown by the distribution drawing (B), the hydrogen concentration isdistributed with the first position Ps as the peak, before theannealing. By diffusing the hydrogen with the annealing, the hydrogenconcentration distribution spreads in the Z-axis direction. The hydrogenconcentration distribution after the annealing has a concentrationdistribution tail S farther on the top surface 21 side than where thefirst position Ps is located. The hydrogen concentration has adistribution that is gentler on the top surface 21 side of the firstposition Ps than on the bottom surface 23 side of the first position Ps.

As shown in the distribution drawing (C), the crystalline defect densitydistribution before the annealing has a shape similar to that of thehydrogen concentration distribution before the annealing. For example,the peak position of the crystalline defect density before the annealingis the same as the peak position Ps of the hydrogen concentration beforethe annealing. By annealing the semiconductor substrate 10, the hydrogendiffuses in the Z-axis direction and terminates the dangling bonds. Asdescribed above, a large amount of hydrogen is present in the vicinityof the hydrogen concentration peak, and therefore almost all of thecrystalline defects in the vicinity of the peak position Ps areterminated.

The distribution drawing (F) shows the carrier concentrationdistribution after the annealing. The distribution drawing (F) is thesame as a portion of the distribution drawing (F) in FIG. 7. As shown bythe distribution drawings (B) and (C), the by implanting the hydrogenions from the top surface 21 side and performing annealing, the highconcentration region 26 and the crystalline defect region 19-1, which isfarther on the top surface 21 side than where the high concentrationregion 26 is located, are formed.

FIG. 13 shows another example of the semiconductor device manufacturingmethod according to the present embodiment. FIG. 13 shows the details ofstep S1006, step S1008, step S1011, and step S1012 shown in FIG. 10B.

As shown in FIG. 13, the semiconductor device manufacturing method ofthe present example includes the step of implanting protons a pluralityof times, such that the positions of the hydrogen concentrationdistribution peaks in the depth direction of the semiconductor substrate10 are different. Specifically, in step S1006, the protons are implantedin the depth direction of the semiconductor substrate 10 through theother main surface of the semiconductor substrate 10, i.e. the bottomsurface 23. In step S1006, the protons are implanted to the positions ofall but one of the plurality of hydrogen peaks to be formed in thebuffer region 20. In the present example, in step S1006, the protons areimplanted in order to the positions Pb4, Pb3, and Pb1. After the protonimplantation of step S1006, the semiconductor substrate 10 is annealedin step S1008. As an example, the annealing temperature is 370° C. andthe annealing time is 5 hours.

Next, in step S1011, protons are implanted through the bottom surface 23to the position Pb2. Furthermore, protons are implanted through the topsurface 21 to the position Ps.

Next, in step S1012, the semiconductor substrate 10 is annealed. As anexample, the annealing temperature is 360° C. and the annealingtemperature is 1 hour. Due to step S1012, the crystalline defect region19-1, the crystalline defect region 19-2, and the high concentrationregion 26 are formed.

FIG. 14 shows another example of the semiconductor device manufacturingmethod according to the present embodiment. The semiconductor devicemanufacturing method shown in FIG. 14 differs from the semiconductordevice manufacturing method shown in FIG. 13 in that the protons areimplanted to the position Pb2 instead of the position Pb1, as in stepS1006 shown in FIG. 13, and also in that the protons are implanted tothe position Pb1 in step S1011. In the present example, the peakposition Kb of the crystalline defect density of the crystalline defectregion 19-2 is arranged farther on the bottom surface 23 side than wherethe position Pb1 is located. In this way, by adjusting the positions ofthe proton implantations in step S1006 and step S1011, it is possible toadjust the peak position Kb of the crystalline defect density.

FIG. 15 shows another example of an outline of the semiconductor devicemanufacturing method according to the present embodiment. Thesemiconductor device manufacturing method of the present example differsfrom the example of FIG. 10B in that an annealing step is includedbetween the step of implanting the protons from the top surface 21 andthe step of implanting the protons from the bottom surface 23 in stepS1011 shown in FIG. 10B. Steps S1002 to S1008 are the same as in theexample shown in FIG. 10B.

In step S1011-1 in the present example, the protons are implanted fromthe bottom surface 23. After step S1011-1, annealing is performed instep S1012-1. The annealing temperature in step S1012-1 is lower thanthe annealing temperature in step S1008. The annealing time in stepS1012-1 may be shorter than the annealing time in step S1008. Thisannealing may be at 360° C. for 1 hour, for example.

Next, in step S1011-2, the protons are implanted through the top surface21. After step S1011-2, annealing is performed in step S1012-2. Theannealing temperature in step S1012-2 is lower than the annealingtemperature in step S1012-1. It should be noted that the annealingtemperature in step S1012-2 is preferably higher than the solderingtemperature in the chip soldering process. Furthermore, the order ofstep S1011-1 and step S1011-2 may be switched.

FIG. 16 is a diagram describing the step of forming the crystallinedefect region 19 and the high concentration region 26 by implantinghydrogen ions (protons in the present example) from the top surface 21side of the semiconductor substrate 10. The region into which protonsare not to be implanted is covered by a mask 110 such as a photoresist.The mask 110 may be provided on the emitter electrode 52. The thicknessT110 of the mask 110 is sufficiently greater than the depth (range) towhich the protons are implanted into the semiconductor substrate 10. Forexample, in a case where the proton range is 8 μm, the thickness T110 isgreater than or equal to 33 μm.

In the proton implantation step, the hydrogen ions may be implanted withan acceleration energy causing a range of 8 μm or more from the topsurface 21 of the semiconductor substrate 10. In this way, it ispossible to form the crystalline defect region 19 below the bottom endof each trench portion. The proton acceleration energy may be greaterthan or equal to 600 keV, greater than or equal to 1.0 MeV, or greaterthan or equal to 1.5 MeV. In this way, it is possible to make the rangeof the protons greater than or equal to 8 μm. In a case where theacceleration energy is 1.0 MeV, the proton range is approximately 16 μm,for example. In a case where the acceleration energy is 1.5 MeV, theproton range is approximately 30 μm, for example.

The proton acceleration energy may be greater than or equal to 5.0 MeV.In a case where the acceleration energy is 5.0 MeV, the proton range isapproximately 215 μm, for example. In this case, the protons can beimplanted to a deeper position. Furthermore, even when the protons areimplanted from the bottom surface 23 side of the semiconductor substrate10, the protons can be implanted to the vicinity of the bottom ends ofthe trench portions. Yet further, even before the process of thinning bygrinding the bottom surface 23 of the semiconductor substrate 10, it ispossible to implant the protons through the bottom surface 23 of thesemiconductor substrate 10 and implant the protons to the vicinity ofthe bottom ends of the trench portions. After the proton implantationthrough the bottom surface 23 of the semiconductor substrate 10, thebottom surface 23 of the semiconductor substrate 10 may be ground.

The proton acceleration energy may be less than or equal to 11.0 MeV orless than or equal to 5.0 MeV. In this way, it is possible to restrictthe implantation of protons to an excessively deep position.Furthermore, it is possible to restrict protons from penetrating throughthe semiconductor substrate 10. The proton acceleration energy may beless than or equal to 2.0 MeV. In a case where the acceleration energyis 2.0 MeV, the proton range is approximately 47 μm, for example.

The proton dose amount may be greater than or equal to 1.0×10¹²/cm². Inthis way, the defects are formed with a sufficient density. Furthermore,the proton dose amount may be less than or equal to 1.0×10¹⁵/cm². Inthis way, even when the protons are implanted from the top surface 21 ina range of 8 μm, for example, it is possible to restrict the effect thatthe crystalline defect density has on the anode region 14 or the baseregion 17.

FIG. 17 is s a diagram describing the step of forming the crystallinedefect region 19 and the high concentration region 26 by implantinghydrogen ions (protons in the present example) from the bottom surface23 side of the semiconductor substrate 10. The region into which protonsare not to be implanted is covered by the mask 110 such as aphotoresist. The mask 110 may be provided on the collector electrode 24.The thickness T110 of the mask 110 is sufficiently greater than thedepth (range) to which the protons are implanted into the semiconductorsubstrate 10.

In a case where the mask 110 is an organic film such as a photoresist,with the hydrogen ion implantation depth being X1 (μm), the lower limitvalue Y1 (μm) for the thickness T110 of the mask 110 may be expressedrelative to X1 (μm), as shown by the relational expression(Expression 1) shown below.

Y1=5.52317×(X1)^(0.79538)  Expression 1:

In this way, the region covered by the mask 110 can be sufficientlyshielded from the hydrogen ions. In a case where the mask 110 is anorganic film such as a photoresist, with the acceleration energy at thetime of the hydrogen ion implantation being E1 (eV), the lower limitvalue Y2 (μm) of the thickness T110 of the mask 110 may be expressedrelative to E1 (eV), as shown by the relational expression (Expression2) shown below.

Y2=1.07515×10⁻¹¹×(E1)²+3.83637×10⁻⁵×(E1)  Expression 2:

Based on the above, the region covered by the mask 110 can besufficiently shielded from the hydrogen ions.

In the proton implantation step, the hydrogen ions may be implanted withan acceleration energy that causes the distance between the protonimplantation position and the top surface 21 of the semiconductorsubstrate 10 to be greater than or equal to 8 μm. The protonacceleration energy may be greater than or equal to 2.0 MeV, greaterthan or equal to 3.0 MeV, or greater than or equal to 4.0 MeV. Byadjusting the acceleration energy, it is possible to form the highconcentration region 26 on the top surface 21 side of the semiconductorsubstrate 10. The high concentration region 26 may be formed at theposition of the accumulation region 16.

FIG. 18 shows distribution diagrams, in the depth direction, of the netdoping concentration (A), the hydrogen concentration (B), thecrystalline defect density (C), the carrier lifetime (D), the carriermobility (E), and the carrier concentration (F) in the semiconductordevice 100 shown in FIG. 17. As described above, in the present example,the high concentration region 26 is formed by implanting hydrogen ionsfrom the bottom surface 23 of the semiconductor substrate 10.

As shown by the distribution drawing (A), there may be a region in whichthe net doping concentration is higher than the concentration N₀, to aposition Pf that is farther on the top surface 21 side than where theposition Pb4 is located. The hydrogen ions pass through thesemiconductor substrate 10, from the bottom surface 23 side to theposition Ps, and crystalline defects that are mainly vacancies anddouble vacancies are formed. Since the hydrogen concentration from theposition Pb4 to the position Pf is sufficiently high, the dangling bondsof the crystalline defects are terminated by the hydrogen, and hydrogendonors are formed.

As shown by the distribution drawing (B), the hydrogen concentration hasa peak at the position Ps. The hydrogen concentration distribution ofthe present example has a tail S from the peak position Ps toward onemain surface (the bottom surface 23 in the present example). Thehydrogen concentration between the position Ps and the position Pb4 maybe higher than the hydrogen concentration in the anode region 14.

As shown by the distribution drawing (C), the crystalline defect densitydistribution has a peak at the position Ks. The crystalline defectdensity distribution has a tail SV1 from the position Ks toward thebottom surface 23, and a tail SV2 from the position Ks toward the topsurface 21. The tail SV1 of the present example is gentler than the tailSV2. The region in which the crystalline defect density is higher thanthe concentration Nr₀ is the region from the position Pr to the positionPf.

As shown by the distribution drawing (D), the carrier lifetimedistribution has a peak at the position Ks. The carrier lifetimedistribution has a tail Sτ1 from the position Ks toward the bottomsurface 23, and a tail Sτ2 from the position Ks toward the top surface21. The tail Sτ1 of the present example is gentler than the tail Sτ2.The region in which the carrier lifetime is lower than τ₀ is the regionfrom the position Pr to the position Pf.

As shown by the distribution drawing (E), the carrier mobilitydistribution has a peak at the position Ks. The carrier mobilitydistribution has a tail Sμ1 from the position Ks toward the bottomsurface 23, and a tail Sμ3 from the position Ks toward the top surface21. The tail Sμ1 of the present example is gentler than the tail Sμ3.The region in which the carrier mobility is less than μ₀ is the regionfrom the position Pr to the position Pf.

As shown by the distribution drawing (F), the carrier concentrationdistribution has a peak at the position Ks. The carrier concentrationdistribution has a tail SN1 from the position Ks toward the bottomsurface 23, and a tail SN3 from the position Ks toward the top surface21. The tail SN1 of the present example is gentler than the tail SN3.The tails SV1, Sτ1, Sμ1, and SN1 of the present example may reach thebuffer region 20, but do not need to reach the buffer region 20.

While the embodiments of the present invention have been described, thetechnical scope of the invention is not limited to the above describedembodiments. It is apparent to persons skilled in the art that variousalterations and improvements can be added to the above-describedembodiments. It is also apparent from the scope of the claims that theembodiments added with such alterations or improvements can be includedin the technical scope of the invention.

The operations, procedures, steps, and stages of each process performedby an apparatus, system, program, and method shown in the claims,embodiments, or diagrams can be performed in any order as long as theorder is not indicated by “prior to,” “before,” or the like and as longas the output from a previous process is not used in a later process.Even if the process flow is described using phrases such as “first” or“next” in the claims, embodiments, or diagrams, it does not necessarilymean that the process must be performed in this order.

LIST OF REFERENCE NUMERALS

10: semiconductor substrate, 11: well region, 12: emitter region, 14:anode region, 15: contact region, 16: accumulation region, 17: baseregion, 18: drift region, 19: crystalline defect region, 19-1:crystalline defect region, 19-2: crystalline defect region, 20: bufferregion, 21: top surface, 22: collector region, 23: bottom surface, 24:collector electrode, 26: high concentration region, 27:bottom-surface-side electrode, 29: extending portion, 30: dummy trenchportion, 31: connecting portion, 32: dummy dielectric, 34: dummyconducting portion, 38: interlayer dielectric film, 39: extendingportion, 40: gate trench portion, 41: connecting portion, 42: gatedielectric, 44: gate conducting portion, 48: gate runner, 49: contacthole, 50: gate metal layer, 52: emitter electrode, 53: top-surface-sideelectrode, 54: contact hole, 56: contact hole, 58: barrier metal, 60:first mesa portion, 62: second mesa portion, 64: third mesa portion, 70:transistor portion, 74: top-surface-side lifetime control region, 78:bottom-surface-side lifetime control region, 80: diode portion, 81:extending region, 82: cathode region, 90: interface portion, 92: edgetermination structure portion, 100: semiconductor device, 110: mask,116: gate pad, 118: emitter pad, 120: active portion, 140: peripheraledge, 150: semiconductor device, 200: semiconductor device, 274:top-surface-side lifetime control region

What is claimed is:
 1. A semiconductor device manufacturing method,comprising: a step of implanting hydrogen ions in a depth direction of asemiconductor substrate through one main surface of the semiconductorsubstrate; and a step of annealing the semiconductor substrate at afirst temperature to reduce crystalline defects generated at a positionwhere the hydrogen ion implantation causes a maximum hydrogenconcentration, thereby forming a position where a defect density ofcrystalline defects formed by the hydrogen ion implantation is at amaximum value to be closer to the one main surface than where a positionof the maximum hydrogen concentration is located.
 2. The semiconductordevice manufacturing method according to claim 1, further comprising:before the step of implanting hydrogen ions in the depth direction ofthe semiconductor substrate through the one main surface side of thesemiconductor substrate: a step of implanting hydrogen ions in the depthdirection of the semiconductor substrate through the other main surfaceside of the semiconductor substrate; and a step of annealing thesemiconductor substrate, into which the hydrogen ions have beenimplanted through the other main surface, at a second temperature thatis higher than the first temperature.
 3. The semiconductor devicemanufacturing method according to claim 2, wherein the step ofimplanting hydrogen ions in the depth direction of the semiconductorsubstrate through the other main surface of the semiconductor substrateincludes a step of implanting the hydrogen ions a plurality of times,such that peaks of a concentration distribution of the hydrogen ions areat different positions in the depth direction of the semiconductorsubstrate.
 4. The semiconductor device manufacturing method according toclaim 1, further comprising: a step of forming the semiconductorsubstrate into chips after the step of annealing at the firsttemperature; and a soldering step of soldering the semiconductorsubstrate that has been formed into chips at a third temperature onto acircuit board, wherein the third temperature is lower than the firsttemperature.
 5. The semiconductor device manufacturing method accordingto claim 1, wherein in the step of implanting the hydrogen ions, thehydrogen ions are implanted with an acceleration energy resulting in arange of 8 μm or more from the one main surface of the semiconductorsubstrate.
 6. The semiconductor device manufacturing method according toclaim 1, wherein an acceleration energy in the step of implanting thehydrogen ions is greater than or equal to 1.0 MeV.
 7. The semiconductordevice manufacturing method according to claim 6, wherein theacceleration energy is greater than or equal to 1.5 MeV.
 8. Thesemiconductor device manufacturing method according to claim 1, whereinan acceleration energy in the step of implanting the hydrogen ions isless than or equal to 11.0 MeV.
 9. The semiconductor devicemanufacturing method according to claim 8, wherein the accelerationenergy is less than or equal to 5.0 MeV.
 10. The semiconductor devicemanufacturing method according to claim 8, wherein the accelerationenergy is less than or equal to 2.0 MeV.
 11. The semiconductor devicemanufacturing method according to claim 1, wherein a dose amount of thehydrogen ions in the step of implanting the hydrogen ions is greaterthan or equal to 1.0×10¹²/cm².
 12. The semiconductor devicemanufacturing method according to claim 1, wherein a dose amount of thehydrogen ions in the step of implanting the hydrogen ions is less thanor equal to 1.0×10¹⁵/cm².